Question

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

Answer 1

Given that x+y=5

cube both sides:

(x+y)^3=x^3+y^3+3xy(x+y)

125=x^3+y^3+3xy(5)

hence

x^3+y^3+15xy=125

so the required expression is x^3+y^3+15xy-125=125–125=0

I hope this will help you please mark my answer as brainliest answer.