ctets15p2 q59
0. If 4x2 + 12xy -8x + 9ysup>2 -12y = (ax + by)(ax + by -4), then the value of asup>2 + bsup>2 is
- Option : A
- Explanation : (A) 4x2 + 12xy - 8x + 9y2 - 12y = (ax + by)(ax + by - 4)
⇒ (2x)2 + (3y)2 + 2(2x)(3y) - 4(2x + 3y)
= (ax + by)(ax + by -4)
⇒ (2x + 3y)2 - 4(2x + 3y)
=(ax + by)(ax + by - 4)
⇒ (2x + 3y)(2x + 3y - 4)
= (ax + by)(ax + by - 4)
∴ a=2, b=3
⇒ a2 + b2 = (2) + (3) = 4 + 9 = 13
