Given: 2x + 3y = 13, xy = 6
Cubing 2x + 3y = 13 both sides, we get
(2x + 3y)3 = (13)3
(2x)3 + (3y)3 + 3(2x )(3y) (2x + 3y) = 2197
8x3 + 27y3 + 18xy(2x + 3y) = 2197
8x3 + 27y3 + 18 x 6 x 13 = 2197
8x3 + 27y3 + 1404 = 2197
8x3 + 27y3 = 2197 – 1404
8x3 + 27y3 = 793