应该是 (a+1)^2 = a^2+2*a+1
你所写的式子不符合逻辑...
(a-1)^2 = a^2-2*a+1
(a-1)*(a+1)=a^2-1
(a-1)*b = a*b-b
代数是啥来着我都快忘记了...