Question

expand vy using suitable identity (3x+2y+7)^2​

Answer 1

Answer:

$(x + y + z)2 = (x2 + y2 + z2 + 2xy + 2yz + 2zx) \\ now \: \\ (3x + 2y + 7)2 = (3x)2 + (2y)2 + (7)2 +( 2 \times 3x \times 2y) + (2 \times 2y \times 7) + (2 \times 7 \times 3x) \\ = 9x2 + 4y2 + 49 + 12xy + 28y + 42x \\ = 9x2 + 4y2 + 12xy + 42x + 28y + 49$