Question

3【(a+1)的平方】-5(a+1)(a-1)+2【(a-1)的平方】

用简便方法解答

Answer 1

3(a+1)²-5(a+1)(a-1)+2(a-1)²
=[3(a+1)-(a-1)]*[(a+1)-2(a-1)]
=(3a+3-a+3)*(a+1-2a+2)
=(2a+6)(-a+3)
-2(a+3)(a-3)
=-2(a²-9)
=-2a²+18