(x-1/2)(x^2+1/4)(x+1/2)
=(x-1/2)(x+1/2)(x^2+1/4)
=(x^2-1/4)(x^2+1/4)
=x^4-1/16
(x+y-z)(x+y+z)
=[(x+y)-z][(x+y)+z]
=(x+y)^2-z^2
=x^2+2xy+y^2-z^2
(a-b+c)(a+b-c)
=[a-(b-c)][a+(b-c)]
=a^2-(b-c)^2
=a^2-b^2+2bc-c^2
[2a^2-(a+b)(a-b)][(c-a)(c+a+(b-c)c+b)]
=(2a^2-a^2+b^2)[(c-a)(c+a+bc-c^2+b)]
=(a^2+b^2)[(c-a)(c+a+bc-c^2+b)]……你看下后面的括号对么,题目应该不会出这样的
(a+b+c)^2-(a-b+c)^2
=(a+b+c+a-b+c)(a+b+c-a+b-c)
=(2a+2c)2b
=4ab+4bc