几道因式分解的7年级数学题（高分！！）
\u4e03\u5e74\u7ea7\u6570\u5b66\u9898\u56e0\u5f0f\u5206\u89e32.7²\u00d71.8²-1.2\u00d71.2²
=\uff089\u00d70.3\uff09²\u00d7\uff089\u00d70.2\uff09²-30\u00d70.2²\u00d7\uff084\u00d70.3\uff09²
=9²\u00d79²\u00d70.3²\u00d70.2²-30\u00d74²\u00d70.3²\u00d70.2²
=\uff089²\u00d79²-30\u00d74²\uff09\u00d70.3²\u00d70.2²
=6081\u00d70.09\u00d70.04
=21.8916
1. a\uff08x\u5e73\u65b9-2x\uff09\u5e73\u65b9-2ax\uff082-x\uff09+a
=a[(x^2-2x)^2+2(x^2-2x)+1]
=a(x^2-2x+1)^2
=a(x-1)^4
2. \uff08t\u5e73\u65b9+2t\uff09\u5e73\u65b9+2\uff08t\u5e73\u65b9+2t\uff09+1
\u4ee4t^2+2t=x
\u539f\u5f0f=x^2+2x+1=(x+1)^2
(x+1)^2=(t^2+2t+1)^2=(t+1)^4
\u5f53t=-3\u65f6 (t+1)^4 =(-3+ 1)^4=(-2)^4=16
3. x\u5e73\u65b9+2\uff08k-3\uff09x+25
=(x+-5)^2=x^2+-2*1*5x+5^2
\uff08k-3)=5 k=8
k-3=-5 k = -2
=(7a-8b+2x)(7a-8b-2x)
X^2(x-4)+y^2(4-x)
=(x^2-y^2)(x-4)
=(x+y)(x-y)(x-4)
a^4-81
=(a^2+9)(a^2-9)
=(a^2+9)(a+3)(a-3)
11(a-b)+11/1(b-a)^3
=11(a-b)[1-121/1(b-a)^2]
=11(a-b)[1+11/1(b-a)][1-11/1(b-a)]
9(a-b)^2+12(a-b)+4
=[3(a-b)+2]^2
(x^2+y^2)^2-4X^2Y^2
=(x^2+y^2+2xy)(x^2+y^2-2xy)
=(x+y)^2(x-y)^2
(a-b）^3-4ab（b-a）
=(a-b)[(a-b)^2+4ab]
=(a-b)(a^2-2ab+b^2+4ab)
=(a-b)(a^2+2ab+b^2)
=(a-b)(a+b)^2
16(x-y)^2-25(x+y)^2
=[4(x-y)+5(x+y)][4(x-y)-5(x+y)]
=(9x+y)(-x-9y)
=-(9x+y)(x+9y)
垃圾,复制的一下还说给你分
1.（7a-8b)^2-4x^2 =(7a-8b-2x)(7a-8b+2x)
2.X^2(x-4)+y^2(4-x)=x^2(x-4)-y^2(x-4)=(x-4)(x^2-y^2)=(x-4)(x-y)(x+y)
3.a^4-81 =(a^2+9)(a^2-9)=(a^2+9)(a^2+3)(a^2-3)
4.11(a-b)+11/1(b-a)^3=11(a-b)-11/1(a-b)^3=(a-b)(11-11/1(a-b)^2)=11/1(a-b)(11^2-(a-b)^2)=11/1(a-b)(11+a-b)(11-a+b)【P.S11/1等于11分之1哈~】
5.9(a-b)^2+12(a-b)+4 =(3(a-b)+2)^2
6.(x^2+y^2)^2-4X^2Y^2 =x^4+y^4+2x^2y^2-4x^2y^2=x^4+y^4-2x^2y^2=(x^2-+y^2)^2=(x+y)^2(x-y)^2
7.(a-b）^3-4ab（b-a)=(a-b）^3+4ab（a-b)=(a-b)((a-b)^2+4ab)=(a-b)(a^2+b^2-2ab+4ab)=(a-b)(a+b)^2
8.16(x-y)^2-25(x+y)^2 =(4x-4y)^2-(5x+5y)^2=(4x-4y-5x-5y)(4x-4y+5x+5y)=(-x-9y)(9x+y)=-(x+9y)(9x+y)
i agree with the NO.1
（7a-8b)^2-4x^2
=(7a-8b+2x)(7a-8b-2x)
X^2(x-4)+y^2(4-x)
=(x^2-y^2)(x-4)
=(x+y)(x-y)(x-4)
a^4-81
=(a^2+9)(a^2-9)
=(a^2+9)(a+3)(a-3)
11(a-b)+11/1(b-a)^3
=11(a-b)[1-121/1(b-a)^2]
=11(a-b)[1+11/1(b-a)][1-11/1(b-a)]
9(a-b)^2+12(a-b)+4
=[3(a-b)+2]^2
(x^2+y^2)^2-4X^2Y^2
=(x^2+y^2+2xy)(x^2+y^2-2xy)
=(x+y)^2(x-y)^2
(a-b）^3-4ab（b-a）
=(a-b)[(a-b)^2+4ab]
=(a-b)(a^2-2ab+b^2+4ab)
=(a-b)(a^2+2ab+b^2)
=(a-b)(a+b)^2
16(x-y)^2-25(x+y)^2
=[4(x-y)+5(x+y)][4(x-y)-5(x+y)]
=(9x+y)(-x-9y)
=-(9x+y)(x+9y)
(*^__^*) 嘻嘻……
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1.解:（7a-8b)^2-4x^2
=(7a-8b+2x)(7a-8b-2x)
2.解:X^2(x-4)+y^2(4-x)
=x^2(x-4)-y^2(x-4)
=(x-4)(x^2-y^2)
=(x-4)(x-y)(x+y)
3.解:a^4-81
=(a^2-9)(a^2+9)
=(a-3)(a+3)(a^2+9)
4.解：11(a-b)+11/1(b-a)^3
=11(a-b)[1-121/1(b-a)^2]
=11(a-b)[1+11/1(b-a)][1-11/1(b-a)]
5.解:9(a-b)^2+12(a-b)+4
=[3(a-b)+2]^2
6.解:(x^2+y^2)^2-4X^2Y^2
=(x^2+y^2)^2-4x^2y^2
=(x^2+y^2+2xy)(x^2+y^2-2xy)
=(x+y)^2(x-y)^2
(a-b）^3-4ab（b-a）
7.解：16(x-y)^2-25(x+y)^2
=[4(x-y)+5(x+y)][4(x-y)-5(x+y)]
=(9x+y)(-x-9y)
=-(9x+y)(x+9y)
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