Question

If x² – y² = 8 and x²+ y² = 4, then what is the value of x⁴ – y⁴?

Answer 1

x^2 - y^2 = 8
x^2 + y^2 = 4
Therefore:   (x^2 - y^2  ) * (x^2 + y^2 ) = 8 *4
Expanded:  x^4 + x^2 y^2 - x^2 y^2 - y^4 = 32
So: x^4 - y^4 = 32