Equation

colakumarfanta wrote:If x = 0 and x = sqrt(8xy-16y^2) , then, in terms of y, x = ?
A. – 4y
B. y/4
C. y
D. 4y
E. 4y^2

OA D

We can take 8 x y – 16 y^2 = 0 or 8 x y = 16 y^2 , but if x is already 0, y should also be 0 to hold the stem as true, and in that case, division by either x or y is not valid, and the question cannot be answered. I am not convinced with the contents supplied to work on, it's making me limcakumarthumsup, huh!

sanju09 wrote:

colakumarfanta wrote:If x = 0 and x = sqrt(8xy-16y^2) , then, in terms of y, x = ?
A. – 4y
B. y/4
C. y
D. 4y
E. 4y^2

OA D

We can take 8 x y – 16 y^2 = 0 or 8 x y = 16 y^2 , but if x is already 0, y should also be 0 to hold the stem as true, and in that case, division by either x or y is not valid, and the question cannot be answered. I am not convinced with the contents supplied to work on, it's making me limcakumarthumsup, huh!

And if x ≠ 0, then x^2 = 8 x y – 16 y^2

Or x^2 – 8 x y + 16 y^2 = 0

Or x^2 – 4 x y – 4 x y + 16 y^2 = 0

Or (x – 4 y) ^2 = 0

Or [spoiler]x = 4 y

D[/spoiler]