数学公因式法告诉我第一题的8个小题，关键、重点是要你们写出过程，我特别想看过程！

显示全部楼层 · 2013-3-3 17:26:46

1.x2-81解:原式=(x+9)(x-9)2.1/4×a2-b2解:原式=1/4(a+b)(a-b)3.9(x-y)2-25解:原式=[3(x-y)+5][3(x-y)-5]4.(x2-y)2-(2y-2)2解:原式=[(x2-y)+(2y-2)][(x2-y)-(2y-2)]
=(x2-y+2y-2)(x2-y-2y+2)
=(x2+y-2)(x2-3y+2)5.x^4-81解:原式=(x2+9)(x2-9) ...

千问 · 2013-3-3 17:26:46

1.（x+9)(x-9)2.(1/2a+b)(1/2a-b)3. 9(x-y)^2-25(平方差公式)=[3(x-y)]^2-5^2=[3(x-y)+5][3(x-y)+5]=(3x-3y+5)(3x-3y-5)3.(x2+9)(x2-9)4(x2-y+2y-2)(x2-y-2y+2)=(x2+y-2)(x2-3y+2)5.(...

千问 · 2013-3-3 17:26:46

x^2-81=x^2-9^2=(x+9)*(x-9)1/4 a^2-b^2=(1/2a)^2-b^2=(1/2 a+b)(1/2 a-b)9(x-y)^2-25=[3(x-y)]^2-5^2=(3x-3y+5)(3x-3y-5)(x^2-y)^2-(2y-2)^2=(x^2-y+2y-2)(x^2-y-2y+2)=(x^2+y-2)(x^2-3...

千问 · 2013-3-3 17:26:46

(1)=x^2-9^2=(x+9)(x-9);(3)=[3(x-y)]^2-5^2=[3(x-y)+5][3(x-y)-5]=(3x-3y+5)(3x-3y-5)(5)=(x^2)^2-9^2=(x^2+9)(x^2-9)=(x^2+9)(x^2-3^2)=(x^2+9)(x+3)(x-3)(7)=[(a^2-2b)+(1-2b)][(a^2-2...

千问 · 2013-3-3 17:26:46

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