Question

先化简再求值:(a+b)^2+(a-b)^2+(-2a+b)(a+2b)其中a=2/3,b=1/2

Answer 1

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

=a^2+2ab+b^2+a^2-2ab+b^2-2a^2-2b^2+5ab

=5ab=5*2/3*1/2=5/3