Question

If a+b=10and ab=21find the value of a³+b³

Answer 1

a+b=10

ab=21

a^3+b^3=?

a^3+b^3

=(a+b)(a^2+b^2-ab)

since (a+b)^2=a^2+b^2+2ab

so when we subtract above equation by ab then it will a^2+b^2-ab

=10{(a+b)^2-3ab}

=10{10^2-3(21)}

=10(100-63)

=10×37

=370