Question

if x-y=5 and xy=84 find x^3-y^3

Answer 1

x³ - y³ = (x - y) (x² + xy + y²)
x³ - y³ = 5 (x² + y² + 84)
x³ - y³ = 5 ((x - y)² + 2xy + 84)
x³ - y³ = 5 (5² + 2 . 84 + 84)
x³ - y³ = 5 . 257
x³ - y³ = 1.285