If x^2 -7x=144 , and y and n are integers such that y^n=x , which of the following CANNOT be a value for y
A)-9
B)16
C)4
D)-3
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GMATGuruNY
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x² - 7x - 144 = 0Hmna wrote:If x^2 -7x=144 , and y and n are integers such that y^n=x , which of the following CANNOT be a value for y
A)-9
B)16
C)4
D)-3
(x-16)(x+9) = 0
x=16 or x=-9.
Since y^n = x, y^n = 16 or y^n = -9.
Options for y: -9, 16, 4, -3.
The option in red is not possible.
There is no positive integer n such that (-3)^n = 16 or (-3)^n = -9.
The correct answer is D.
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x² - 7x = 144
x² - 7x - 144 = 0
(x + 9) * (x - 16) = 0
So x = -9 or x = 16.
If y = -9 and n = 1, then x = -9: cross out (A).
If y = 16 and n = 1, then x = 16: cross out (B).
If y = 4 and n = 2, then x = 16: cross out (C).
By process of elimination, (D) is the right answer.
x² - 7x - 144 = 0
(x + 9) * (x - 16) = 0
So x = -9 or x = 16.
If y = -9 and n = 1, then x = -9: cross out (A).
If y = 16 and n = 1, then x = 16: cross out (B).
If y = 4 and n = 2, then x = 16: cross out (C).
By process of elimination, (D) is the right answer.
