Question

Find value of x^3+y^3+15xy-125,if x+y=5

Answer 1

its easy just apply formula of a^3 + b^3 =(a+b)^3 -3ab(a+b)
applying this
(x+y)^3 - 3xy(x+y) + 15xy -125
by putting the value of x+y=5
the answer will be equal to zero

Answer 2

$(x+y) ^{3} =5 ^{3} \\ x^{3} +y ^{3} +3xy(x+y)=125 \\ substitue (x+y)$ value i  n the equation  ans u will get is 0