Question

七下数学题？？？

（x+y）^2-z^=
a^2-(b-c)^2=
(x-y)^3-x+y=
16(x+y)^2-25(x-y)^2=

Answer 1

解：只要懂得平方差公式就不难做啦！a²-b²=（a+b）×（a-b）
（x+y）^2-z^2=（x+y+z）×（x+y-z）
a^2-(b-c)^2=（a+b-c）×（a-b+c）
(x-y)^3-x+y= (x-y)^3-（x-y）=（x-y）×[（x-y）²-1]=（x-y）×（x-y+1）×（x-y-1）
16(x+y)^2-25(x-y)^2=[4（x+y）]²-[5（x-y）]²=（9x-y）×（y-x）

Answer 2

（x+y）^2-z^2
=(x+y+z)(x+y-z)

a^2-(b-c)^2
=(a-b+c)(a+b-c)

(x-y)^3-x+y
=(x-y)^3-(x-y)
=(x-y)[(x-y)^2-1]
=(x-y)(x-y+1)(x-y-1)

16(x+y)^2-25(x-y)^2
=[4(x+y)]^2-[5(x-y)]^2
=[4(x+y)+5(x-y)]*[4(x+y)-5(x-y)]
=(4x+4y+5x-5y)(4x+4y-5x+5y)
=(9x-y)(9y-x)

Answer 3

=(x+y+z)(x+y-z)

=(a-b+c)(a+b-c)

=(x-y)(x-y+1)(x-y-1)

=(9x-y)(9y-x)

Answer 4

化简么？