Question

find the value of x³+y³+ 15xy-125 if x + y =5​

Answer 1

x + y =5

So x = 5 - y

(5-y)³ + y³ +15y(5-y) - 125

125 - 75y + 15y² - y³ + y³ +75y - 15y² - 125

So answer is 0 — ( All terms of opposite sign get cancelled)

Hope it helps you