Question

If (3x – 5y) = 10 and xy=5, then find the value of 9x2 + 25y2.

Answer 1

Step-by-step explanation:

We know that 3x + 5y = 11 and xy = 2

Upon squaring on both sides of the given expression, we get

(3x + 5y)2 = 112

(3x)2 + (5y)2 + 2(3x)(5y) = 121

9x2 + 5y2 + 2 (15xy) = 121 (since xy=2)

9x2 + 5y2 + 2(15(2)) = 121

9x2 + 5y2 + 60 = 121

9x2 + 5y2 = 121-60

9x2 + 5y2 = 61

Hope it will help