Question

1.(ax+b)(cx+d)2.(-3x+y)(-3x-y)3.(x+2)(x-1)-(x-2)(x+3)4.(x-2)

Answer 1

1.(ax+b)(cx+d)

=ax(cx+d)+b(cx+d)

=acx2+adx+bcx+bd

=acx平方+(ad+bc)x+bd

2.(-3x+y)(-3x-y)

=(3x-y)(3x+y)

=9x平方+y平方

3.(x+2)(x-1)-(x-2)(x+3)

=x平方+x-2-(x平方+x-6)

=4

4.原式=x(x+2)(x-2)+x(x+2)(x-2)

=2x(x+2)(x-2)

5.因为(x-5)(x+20)=X平方+15x-100

=x平方+mx+n

所以m=15,n=-100