Question

(-2x-1)²-4(x-1)(x+2)

(-2x-1)²-4(x-1)(x+2)，怎么算？

Answer 1

原式=(2x+1)²-4(x²+x-2)
=4x²+4x+1-4x²-4x+8
=9

追问

我看不懂的就是为什么(x-1)(x+2）会等于(x²+x-2)

追答

=x(x+2)-1*(x+2)
=x²+2x-x-2
=x²+x-2
采纳吧

Answer 2

=4x²+4x+1-4(x²+x-2)
=4x²+4x+1-4x²-4x+8
=9