Question

If 9x²- 30xy+ (N+9) y² is a perfect square, then N²= how much? ​

Answer 1

Given:

9x² + 30xy + ( N + 9 )y² is a perfect square

Let ( N + 9 ) = M

= $(3x)^{2} + 2*3x*5y + M^{2}y^{2}$

This expression can be written in the form of (a + b)² only if M = 5

i.e., N+9 = 5

N = (-4)

HOPE IT HELPS !!