Question

已知a+b=2,a的三次方+6ab+6b的三次方

Answer 1

因为(a+b)^3=a^3+3a^2b+3ab^2+b^3=8,

所以a^3+b^3=8-3a^2b-3ab^2

代人,得,

a的三次方+6ab+6b的三次方

=a^3+b^2+6ab

=(8-3a^2b-3ab^2)+6ab

=8-3ab(a+b)+6ab

=8-6ab+6ab

=8