Question

If 4x - 9y =10 and xy = -1, then find the value of 16x2+81y2.

Answer is 28​

Answer 1

Answer:

(4x - 9y)^2 = 16x^2 + 81y^2 - 2.4x.9y

10×10 = 16x^2 + 81y^2 - 72xy

100 = 16x^2 + 81 y^2 - 72×1

16x^2 + 81y^2 = 100+72 = 172 Ans