Question

1. If 3x-7y=10 and xy=1, find 9x2+49y2

Answer 1

(a-b)^2=a^2 - 2*a*b + b^2
(3x-7y)^2=(10)^2
9x^2 - 2*3x*7y + 49y^2 = 100
9x^2 - 2*21*1 + 49y^2 = 100
9x^2 + 49y^2 = 100-42
=58.

Answer 2

Answer: 58

Square both sides of eq (3x-7y)^2=10^2

Add the value of x and you get the ans