Question

若a^2+b^2-2a+4b+5=0,则a(ab^2+2ab-a^3b)的值为

Answer 1

因为：a^2+b^2-2a+4b+5=0 化简为：(a-1)^2+(b+2)^2=0.所以解得：a=1,b=-2.代入下式：a(ab^2+2ab-a^3b) =1(1x4-4+2) =2.