Question

已知a+ b=4,a平方+ b平方=12,求a的三次方 +b的三次方

Answer 1

(a^3+b^2)

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

=4(12-ab)

=48-4ab

=48-2[(a+b)^2-(a^2+b^2)]

=48-2(16-12)

=40