1.
m^3/(-m^2)m
=m^3/(-m^3)
=-1
2.
(2a+1)(a-3)
=2a^2-6a+a-3
=2a^2-5a-3
2(a+1)(a-1)
=2(a^2-1)
=2a^2-2
3.
(a-b+2)(a+b-2)
=[a+(2-b)][a-(2-b)]
=a^2-(2-b)^2
=a^2-(b^2-2b+4)
=a^2-b^2+2b-4
4.
(x-1)(x+6)-(x+1)^2
=x^2+5x-6-(x^2+2x+1)
=3x-7
1.
2(a-b)-a+b
=2(a-b)-(a-b)
=(a-b)
2.
(a^2+b^2)^2-4a^2b^2
=(a^2-b^2)^2
3.
2x^2-x+1/8
=2(x^2-01/2*x+1/16)
=2[x^2-2*1/4*x+(1/4)^2]
=2(x-1/4)^2
用到的公式
(a+b)^2=a^2+2ab+b^2
a^2-b^2=(a+b)(a-b)