Which of the following equations is NOT equivalent to 10y^2 = (x+2)(x-2)?
A) 30y^2 = 3x^2 - 12
B) 20y^2 = (2x - 4)(x + 2)
C) 10y^2 + 4 = x^2
D) 5y^2 = x^2 - 2
E) y^2 = (x^2 - 4)/10
OA: D
Which of the following equations is NOT equivalent
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A
B
C
D
E
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Given: 10y^2 = (x+2)(x-2)boomgoesthegmat wrote:Which of the following equations is NOT equivalent to 10y^2 = (x+2)(x-2)?
A) 30y^2 = 3x^2 - 12
B) 20y^2 = (2x - 4)(x + 2)
C) 10y^2 + 4 = x^2
D) 5y^2 = x^2 - 2
E) y^2 = (x^2 - 4)/10
OA: D
Or 10y^2 = x^2 - 4
We can solve it by assuming values of x and y or simply by rearranging the options.
Let us start rearranging the options that look easy first.
A) 30y^2 = 3x^2 - 12 => Cancelling out 3 from both sides, 10y^2 = x^2 - 4
C) 10y^2 + 4 = x^2 => On rearranging, 10y^2 = x^2 - 4
D) 5y^2 = x^2 - 2 => Multiplying by 2 on both sides, 10y^2 = 2x^2 - 4.
This is not equal to 10y^2 = x^2 - 4
We do not need to check for the other options.
Correct Option: D
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Hi All,
We're asked which of the following equations is NOT equivalent to 10y^2 = (x+2)(x-2). This question ultimately comes down to 'rewriting' the given equation, so a little bit of math work is required.
To start, we can rewrite 10y^2 = (x+2)(x-2) as....
10y^2 = x^2 - 4
Answer A) 30y^2 = 3x^2 - 12
If we multiply BOTH sides of the given equation by 3, then we will end up with Answer A.
Answer B) 20y^2 = (2x - 4)(x + 2)
If we multiply BOTH sides of the given equation by 2, then we'll end up with...
20y^2 = 2x^2 - 8
We can then factor the 'right side' into:
2x^2 - 8 = (x+2)(2x-4)....
Thus, we will end up with Answer B.
Answer C) 10y^2 + 4 = x^2
If we add 4 to both sides of the equation, then we'll end up with Answer C.
Answer E) y^2 = (x^2 - 4)/10
If we divide BOTH sides of the given equation by 10, then we'll end up with Answer E.
There's only one answer that is NOT mathematically equivalent...
Final Answer: D
GMAT assassins aren't born, they're made,
Rich
We're asked which of the following equations is NOT equivalent to 10y^2 = (x+2)(x-2). This question ultimately comes down to 'rewriting' the given equation, so a little bit of math work is required.
To start, we can rewrite 10y^2 = (x+2)(x-2) as....
10y^2 = x^2 - 4
Answer A) 30y^2 = 3x^2 - 12
If we multiply BOTH sides of the given equation by 3, then we will end up with Answer A.
Answer B) 20y^2 = (2x - 4)(x + 2)
If we multiply BOTH sides of the given equation by 2, then we'll end up with...
20y^2 = 2x^2 - 8
We can then factor the 'right side' into:
2x^2 - 8 = (x+2)(2x-4)....
Thus, we will end up with Answer B.
Answer C) 10y^2 + 4 = x^2
If we add 4 to both sides of the equation, then we'll end up with Answer C.
Answer E) y^2 = (x^2 - 4)/10
If we divide BOTH sides of the given equation by 10, then we'll end up with Answer E.
There's only one answer that is NOT mathematically equivalent...
Final Answer: D
GMAT assassins aren't born, they're made,
Rich
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Simplifying the stem we have:boomgoesthegmat wrote:Which of the following equations is NOT equivalent to 10y^2 = (x+2)(x-2)?
A) 30y^2 = 3x^2 - 12
B) 20y^2 = (2x - 4)(x + 2)
C) 10y^2 + 4 = x^2
D) 5y^2 = x^2 - 2
E) y^2 = (x^2 - 4)/10
10y^2 = x^2 - 4
Let's analyze each answer choice:
A) 30y^2 = 3x^2 - 12
Dividing by 3 we have:
10y^2 = x^2 - 4
Choice A is equivalent.
B) 20y^2 = (2x - 4)(x + 2)
20y^2 = (2x - 4)(x + 2)
20y^2 = 2x^2 - 8
10y^2 = x^2 - 4
Choice B is equivalent.
C) 10y^2 + 4 = x^2
10y^2 + 4 = x^2
10y^2 = x^2 - 4
Choice C is equivalent.
D) 5y^2 = x^2 - 2
Multiplying by 2 we have:
10y^2 = 2x^2 - 4
Choice D is NOT equivalent.
Answer: D