Question

if x y 8 and xy 15 find the value of x 3 +y 3

Answer 1

x + y = 8
xy = 15
x^3 + y^3 =(x + y)(x^2 - xy + y^2)
8 (x^2 + y^2 - 15)


x^2 + y^2 +2xy = 8^2 = 64
x^2 +y^2 = 64 - 2 (15)
x^2 +y^2 = 64 - 30 = 34


8(34 -15)
8 (19)
152