Question

If 3x^2+3y^2 = 42 and xy = -15, find the value of (x-y)^2

Answer 1

3x² + 3y² = 42

3 ( x² + y² ) = 42

x² + y² = 14

xy = -15 ( given )

(x-y)² = x² + y² - xy

14 - ( -15 )

14 + 15

29