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y=x3+6x2+9x y=x3-6x2+9x y=x3-6x2-9x y=x3+6x2-9x
x= x=3 x1=,x2=3 x1=﹣,x2=﹣3
f (x)=9x+8 f (x)=3x+2 f(x)=-3x-4 f(x)=3x+2或f(x)=-3x-4
2x+3x=9+5 2x﹣3x=9+5 2x﹣3x=﹣9+5 2x﹣3x=9﹣5
2x-4-12x+3=9,-10x=9-4+3,故x=0.8 ; 2x-4-12x+3=9,-10x=9+4-3,故x=-1 ; 2x-4-12x-3=9,-10x=9+4+3,故x=-1.6; 2x-2-12x+1=9,-10x=9+2-1,故x=-1 ;
2(x2-9) 2(x-3)2 2(x+3)(x-3) 2(x+9)(x-9)
(x+9y)(x-9y) (x+3y)(x-3y) (x-3y)2 (x-9y)2
x(x2﹣9) x(x﹣3)2 x(x+3)2 x(x+3)(x﹣3)
3 x-3 =1+2 x , 3 x-9 =1+2 x , 3 x-3 =2+2 x , 3 x-12=2+4 x ;
x2+9 x2-6x+9 x2+6x+9 x2+3x+9
f(x)=9x+8 f(x)=3x+2 f(x)=-3x-4 f(x)=3x+2或f(x)=-3x-4
(3-x)2 (3+x)(3-x) (9-x)2 (9+x)(9-x)
2x+3x=9+5 2x-3x=-9+5 2x-3x=9+5 2x-3x=9-5
(3x+1)(3x-1)=9x2-1 x2-2x+4=(x-2)2 a4-1=(a2+1)(a+1)(a-1) 9x2-1+3x=(3x+1)(3x-1)+3x
2x(x+3)2 2x(x﹣3)2 2x(x2﹣9) 2x(x+3)(x﹣3)
{x|0<x<3} {x|1<x<3} {x|2<x<3}
x2-6x+9=(x-3)2 (x+3)(x-1)=x2+2x-3 x2-9+6x=(x+3)(x-3)+6x 6ab=2a·3b