a^2+b^2+2a+4b+5=0 a^2+2a+1+b^2+4b+4=0 (a+1)^2+(b+2)^2=0所以a+1=0,b+2=0a=-1,b=-2.[（a+b/2）+(a-b/2)^2]*(2a^2-1/2b^2)=[(-1-1)+(-1+1)^2]*(2-1/2*4)=-2*0=0
