Question

if 3x-4y=16 and xy=4,find the value of 9x^2+16y^2​

Answer 1

Squaring on both sides

➡ (3x - 4y)^2 = (16)^2
➡ (3x)^2 + (4y)^2 - 2(3x)(4y) = 256
➡ 9x^2 + 16y^2 - 24xy = 256
➡ 9x^2 + 16y^2 - 24(4) = 256
➡ 9x^2 + 16y^2 - 96 = 256
➡ 9x^2 + 16y^2 = 256 + 96
➡ 9x^2 + 16y^2 = 352