Solve the inequality $frac{2}{x} > 3 x$ [closed]
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I've been slowly losing my mind on how to do this question, any help would be greatly appreciated.
Solve the inequality $$frac{2}{x} > 3 x.$$
algebra-precalculus inequality
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closed as off-topic by Xander Henderson, zz20s, Eevee Trainer, mrtaurho, Claude Leibovici Jan 14 at 7:08
This question appears to be off-topic. The users who voted to close gave this specific reason:
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If this question can be reworded to fit the rules in the help center, please edit the question.
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I've been slowly losing my mind on how to do this question, any help would be greatly appreciated.
Solve the inequality $$frac{2}{x} > 3 x.$$
algebra-precalculus inequality
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closed as off-topic by Xander Henderson, zz20s, Eevee Trainer, mrtaurho, Claude Leibovici Jan 14 at 7:08
This question appears to be off-topic. The users who voted to close gave this specific reason:
- "This question is missing context or other details: Please provide additional context, which ideally explains why the question is relevant to you and our community. Some forms of context include: background and motivation, relevant definitions, source, possible strategies, your current progress, why the question is interesting or important, etc." – Xander Henderson, zz20s, Eevee Trainer, mrtaurho, Claude Leibovici
If this question can be reworded to fit the rules in the help center, please edit the question.
2
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Draw a picture!!!
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– aidangallagher4
Jan 14 at 0:04
add a comment |
$begingroup$
I've been slowly losing my mind on how to do this question, any help would be greatly appreciated.
Solve the inequality $$frac{2}{x} > 3 x.$$
algebra-precalculus inequality
$endgroup$
I've been slowly losing my mind on how to do this question, any help would be greatly appreciated.
Solve the inequality $$frac{2}{x} > 3 x.$$
algebra-precalculus inequality
algebra-precalculus inequality
edited Jan 14 at 0:04
Viktor Glombik
1,3802628
1,3802628
asked Jan 13 at 23:49
Nanji ChoNanji Cho
83
83
closed as off-topic by Xander Henderson, zz20s, Eevee Trainer, mrtaurho, Claude Leibovici Jan 14 at 7:08
This question appears to be off-topic. The users who voted to close gave this specific reason:
- "This question is missing context or other details: Please provide additional context, which ideally explains why the question is relevant to you and our community. Some forms of context include: background and motivation, relevant definitions, source, possible strategies, your current progress, why the question is interesting or important, etc." – Xander Henderson, zz20s, Eevee Trainer, mrtaurho, Claude Leibovici
If this question can be reworded to fit the rules in the help center, please edit the question.
closed as off-topic by Xander Henderson, zz20s, Eevee Trainer, mrtaurho, Claude Leibovici Jan 14 at 7:08
This question appears to be off-topic. The users who voted to close gave this specific reason:
- "This question is missing context or other details: Please provide additional context, which ideally explains why the question is relevant to you and our community. Some forms of context include: background and motivation, relevant definitions, source, possible strategies, your current progress, why the question is interesting or important, etc." – Xander Henderson, zz20s, Eevee Trainer, mrtaurho, Claude Leibovici
If this question can be reworded to fit the rules in the help center, please edit the question.
2
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Draw a picture!!!
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– aidangallagher4
Jan 14 at 0:04
add a comment |
2
$begingroup$
Draw a picture!!!
$endgroup$
– aidangallagher4
Jan 14 at 0:04
2
2
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Draw a picture!!!
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– aidangallagher4
Jan 14 at 0:04
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Draw a picture!!!
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– aidangallagher4
Jan 14 at 0:04
add a comment |
3 Answers
3
active
oldest
votes
$begingroup$
To solve the equation
$$
frac{2}{x} > 3x
$$
we could multiply be $x$ to obtain
$$
2 > 3x^2.
$$
But you have to be careful!
If $x < 0$, the inequality is reversed.
In other words:
$$
frac{2}{x} > 3x
iff begin{cases}
2 < 3x^2 & x < 0 \
2 > 3x^2 & x > 0.
end{cases}
$$
Notice the equation isn't defined for $x = 0$, because you can't divide by $0$.
Case 1: $x > 0$.
Then we have
$$
2> 3x^2
iff x^2 < frac{2}{3}
iff x in left(- sqrt{ frac{2}{3}}, sqrt{ frac{2}{3}}right).
$$
But, since $x > 0$, our first solution interval is $I_1 := left(0, sqrt{ frac{2}{3}}right)$.
Case 2: $x < 0$.
Then we have
$$
2 < 3x^2
iff x^2 > frac{3}{2}
iff x > sqrt{frac{3}{2}} quad text{and} qquad x < -sqrt{frac{3}{2}}
$$
But again, since $x < 0$, our second (and final) solution interval is $I_2 := left(- infty, -sqrt{frac{3}{2}}right)$.
So our solution is $I_1 cup I_2 =left(- infty, -sqrt{frac{3}{2}}right) cup left(0, sqrt{ frac{2}{3}}right)$.
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add a comment |
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We observe that necessarily $xneq 0$ whence we can rewrite the inequality as
$$
frac{2}{x}-3x>0ifffrac{2x-3x^3}{x^2}>0iff 2x-3x^3>0iff x(2-3x^2)>0
$$
which you can solve.
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add a comment |
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Usually you're supposed to give some context and explain what you've tried so far. However, I will take your word that you have been "slowly losing" your mind and give an answer.
Since this is a nonlinear inequality, there is no "cookie cutter" way to solve it. But you can get an idea of what to do by graphing $y_1=2/x$ and $y_2=3x$, and observing where $y_1>y_2$.
See here for a graph with $y_1=2/x$ in red and $y_2=3x$ in blue. Where does the red curve lie above the blue curve?
Well, you can see that there are two intersection points. But the red lies above the blue from $-infty$ up to the first intersection point, and then again from zero to the second intersection point.
To find the intersection points, set $2/x=3x$ and solve.
Can you write down the final answer?
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add a comment |
3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
To solve the equation
$$
frac{2}{x} > 3x
$$
we could multiply be $x$ to obtain
$$
2 > 3x^2.
$$
But you have to be careful!
If $x < 0$, the inequality is reversed.
In other words:
$$
frac{2}{x} > 3x
iff begin{cases}
2 < 3x^2 & x < 0 \
2 > 3x^2 & x > 0.
end{cases}
$$
Notice the equation isn't defined for $x = 0$, because you can't divide by $0$.
Case 1: $x > 0$.
Then we have
$$
2> 3x^2
iff x^2 < frac{2}{3}
iff x in left(- sqrt{ frac{2}{3}}, sqrt{ frac{2}{3}}right).
$$
But, since $x > 0$, our first solution interval is $I_1 := left(0, sqrt{ frac{2}{3}}right)$.
Case 2: $x < 0$.
Then we have
$$
2 < 3x^2
iff x^2 > frac{3}{2}
iff x > sqrt{frac{3}{2}} quad text{and} qquad x < -sqrt{frac{3}{2}}
$$
But again, since $x < 0$, our second (and final) solution interval is $I_2 := left(- infty, -sqrt{frac{3}{2}}right)$.
So our solution is $I_1 cup I_2 =left(- infty, -sqrt{frac{3}{2}}right) cup left(0, sqrt{ frac{2}{3}}right)$.
$endgroup$
add a comment |
$begingroup$
To solve the equation
$$
frac{2}{x} > 3x
$$
we could multiply be $x$ to obtain
$$
2 > 3x^2.
$$
But you have to be careful!
If $x < 0$, the inequality is reversed.
In other words:
$$
frac{2}{x} > 3x
iff begin{cases}
2 < 3x^2 & x < 0 \
2 > 3x^2 & x > 0.
end{cases}
$$
Notice the equation isn't defined for $x = 0$, because you can't divide by $0$.
Case 1: $x > 0$.
Then we have
$$
2> 3x^2
iff x^2 < frac{2}{3}
iff x in left(- sqrt{ frac{2}{3}}, sqrt{ frac{2}{3}}right).
$$
But, since $x > 0$, our first solution interval is $I_1 := left(0, sqrt{ frac{2}{3}}right)$.
Case 2: $x < 0$.
Then we have
$$
2 < 3x^2
iff x^2 > frac{3}{2}
iff x > sqrt{frac{3}{2}} quad text{and} qquad x < -sqrt{frac{3}{2}}
$$
But again, since $x < 0$, our second (and final) solution interval is $I_2 := left(- infty, -sqrt{frac{3}{2}}right)$.
So our solution is $I_1 cup I_2 =left(- infty, -sqrt{frac{3}{2}}right) cup left(0, sqrt{ frac{2}{3}}right)$.
$endgroup$
add a comment |
$begingroup$
To solve the equation
$$
frac{2}{x} > 3x
$$
we could multiply be $x$ to obtain
$$
2 > 3x^2.
$$
But you have to be careful!
If $x < 0$, the inequality is reversed.
In other words:
$$
frac{2}{x} > 3x
iff begin{cases}
2 < 3x^2 & x < 0 \
2 > 3x^2 & x > 0.
end{cases}
$$
Notice the equation isn't defined for $x = 0$, because you can't divide by $0$.
Case 1: $x > 0$.
Then we have
$$
2> 3x^2
iff x^2 < frac{2}{3}
iff x in left(- sqrt{ frac{2}{3}}, sqrt{ frac{2}{3}}right).
$$
But, since $x > 0$, our first solution interval is $I_1 := left(0, sqrt{ frac{2}{3}}right)$.
Case 2: $x < 0$.
Then we have
$$
2 < 3x^2
iff x^2 > frac{3}{2}
iff x > sqrt{frac{3}{2}} quad text{and} qquad x < -sqrt{frac{3}{2}}
$$
But again, since $x < 0$, our second (and final) solution interval is $I_2 := left(- infty, -sqrt{frac{3}{2}}right)$.
So our solution is $I_1 cup I_2 =left(- infty, -sqrt{frac{3}{2}}right) cup left(0, sqrt{ frac{2}{3}}right)$.
$endgroup$
To solve the equation
$$
frac{2}{x} > 3x
$$
we could multiply be $x$ to obtain
$$
2 > 3x^2.
$$
But you have to be careful!
If $x < 0$, the inequality is reversed.
In other words:
$$
frac{2}{x} > 3x
iff begin{cases}
2 < 3x^2 & x < 0 \
2 > 3x^2 & x > 0.
end{cases}
$$
Notice the equation isn't defined for $x = 0$, because you can't divide by $0$.
Case 1: $x > 0$.
Then we have
$$
2> 3x^2
iff x^2 < frac{2}{3}
iff x in left(- sqrt{ frac{2}{3}}, sqrt{ frac{2}{3}}right).
$$
But, since $x > 0$, our first solution interval is $I_1 := left(0, sqrt{ frac{2}{3}}right)$.
Case 2: $x < 0$.
Then we have
$$
2 < 3x^2
iff x^2 > frac{3}{2}
iff x > sqrt{frac{3}{2}} quad text{and} qquad x < -sqrt{frac{3}{2}}
$$
But again, since $x < 0$, our second (and final) solution interval is $I_2 := left(- infty, -sqrt{frac{3}{2}}right)$.
So our solution is $I_1 cup I_2 =left(- infty, -sqrt{frac{3}{2}}right) cup left(0, sqrt{ frac{2}{3}}right)$.
edited Jan 14 at 0:04
answered Jan 13 at 23:52
Viktor GlombikViktor Glombik
1,3802628
1,3802628
add a comment |
add a comment |
$begingroup$
We observe that necessarily $xneq 0$ whence we can rewrite the inequality as
$$
frac{2}{x}-3x>0ifffrac{2x-3x^3}{x^2}>0iff 2x-3x^3>0iff x(2-3x^2)>0
$$
which you can solve.
$endgroup$
add a comment |
$begingroup$
We observe that necessarily $xneq 0$ whence we can rewrite the inequality as
$$
frac{2}{x}-3x>0ifffrac{2x-3x^3}{x^2}>0iff 2x-3x^3>0iff x(2-3x^2)>0
$$
which you can solve.
$endgroup$
add a comment |
$begingroup$
We observe that necessarily $xneq 0$ whence we can rewrite the inequality as
$$
frac{2}{x}-3x>0ifffrac{2x-3x^3}{x^2}>0iff 2x-3x^3>0iff x(2-3x^2)>0
$$
which you can solve.
$endgroup$
We observe that necessarily $xneq 0$ whence we can rewrite the inequality as
$$
frac{2}{x}-3x>0ifffrac{2x-3x^3}{x^2}>0iff 2x-3x^3>0iff x(2-3x^2)>0
$$
which you can solve.
edited Jan 14 at 0:18
answered Jan 13 at 23:53
Foobaz JohnFoobaz John
23k41552
23k41552
add a comment |
add a comment |
$begingroup$
Usually you're supposed to give some context and explain what you've tried so far. However, I will take your word that you have been "slowly losing" your mind and give an answer.
Since this is a nonlinear inequality, there is no "cookie cutter" way to solve it. But you can get an idea of what to do by graphing $y_1=2/x$ and $y_2=3x$, and observing where $y_1>y_2$.
See here for a graph with $y_1=2/x$ in red and $y_2=3x$ in blue. Where does the red curve lie above the blue curve?
Well, you can see that there are two intersection points. But the red lies above the blue from $-infty$ up to the first intersection point, and then again from zero to the second intersection point.
To find the intersection points, set $2/x=3x$ and solve.
Can you write down the final answer?
$endgroup$
add a comment |
$begingroup$
Usually you're supposed to give some context and explain what you've tried so far. However, I will take your word that you have been "slowly losing" your mind and give an answer.
Since this is a nonlinear inequality, there is no "cookie cutter" way to solve it. But you can get an idea of what to do by graphing $y_1=2/x$ and $y_2=3x$, and observing where $y_1>y_2$.
See here for a graph with $y_1=2/x$ in red and $y_2=3x$ in blue. Where does the red curve lie above the blue curve?
Well, you can see that there are two intersection points. But the red lies above the blue from $-infty$ up to the first intersection point, and then again from zero to the second intersection point.
To find the intersection points, set $2/x=3x$ and solve.
Can you write down the final answer?
$endgroup$
add a comment |
$begingroup$
Usually you're supposed to give some context and explain what you've tried so far. However, I will take your word that you have been "slowly losing" your mind and give an answer.
Since this is a nonlinear inequality, there is no "cookie cutter" way to solve it. But you can get an idea of what to do by graphing $y_1=2/x$ and $y_2=3x$, and observing where $y_1>y_2$.
See here for a graph with $y_1=2/x$ in red and $y_2=3x$ in blue. Where does the red curve lie above the blue curve?
Well, you can see that there are two intersection points. But the red lies above the blue from $-infty$ up to the first intersection point, and then again from zero to the second intersection point.
To find the intersection points, set $2/x=3x$ and solve.
Can you write down the final answer?
$endgroup$
Usually you're supposed to give some context and explain what you've tried so far. However, I will take your word that you have been "slowly losing" your mind and give an answer.
Since this is a nonlinear inequality, there is no "cookie cutter" way to solve it. But you can get an idea of what to do by graphing $y_1=2/x$ and $y_2=3x$, and observing where $y_1>y_2$.
See here for a graph with $y_1=2/x$ in red and $y_2=3x$ in blue. Where does the red curve lie above the blue curve?
Well, you can see that there are two intersection points. But the red lies above the blue from $-infty$ up to the first intersection point, and then again from zero to the second intersection point.
To find the intersection points, set $2/x=3x$ and solve.
Can you write down the final answer?
answered Jan 13 at 23:59
Ben WBen W
2,734918
2,734918
add a comment |
add a comment |
2
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Draw a picture!!!
$endgroup$
– aidangallagher4
Jan 14 at 0:04