Phân tích các đa thức sau thành nhân tử
a) \(12x^3+4x^2-27x-9\)
b) \(x^6-x^4+2x^3+2x^2\)
c) \(30ax-34bx-15a+17b\)
d) \(x^3-x^2y-x^2z-xyz\)
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a) \(x^2-xz-9y^2+3yz\)
\(=\left(x^2-9y^2\right)-\left(xz-3yz\right)\)
\(=\left(x-3y\right)\left(x+3y\right)-z\left(x-3y\right)\)
\(=\left(x-3y\right)\left(x+3y-z\right)\)
c) \(x^3+2x^2-6x-27\)
\(=\left(x^3-27\right)+\left(2x^2-6x\right)\)
\(=\left(x-3\right)\left(x^2-3x+9\right)+2x\left(x-3\right)\)
\(=\left(x-3\right)\left(x^2-3x+9+2x\right)\)
\(=\left(x-3\right)\left(x^2-x+9\right)\)
Bài 3:
a: =>(2x-7)(x-2)=0
=>x=7/2 hoặc x=2
b: =>(x-1)(x+2)=0
=>x=1 hoặc x=-2
d: =>2x+3=0
hay x=-3/2
30ax - 34bx - 15a + 17b
=2x(15a-17b)-1(15a-17b)
=(15a-17b)(2x-1).
\(30ax-34bx-15a+17b.\)
\(=2\times\left(15a-17b\right)-1\times\left(15a-17b\right)\)
\(=\left(15a-17b\right)\times\left(2x-1\right)\)
a: =(6x)^2-(3x-2)^2
=(6x-3x+2)(6x+3x-2)
=(9x-2)(3x+2)
d: \(=\left[\left(x+1\right)^2-\left(x-1\right)^2\right]\left[\left(x+1\right)^2+\left(x-1\right)^2\right]\)
\(=4x\cdot\left[x^2+2x+1+x^2-2x+1\right]\)
=8x(x^2+1)
e: =(4x)^2-2*4x*3y+(3y)^2
=(4x-3y)^2
f: \(=-\left(\dfrac{1}{4}x^4-2\cdot\dfrac{1}{2}x^2\cdot2y^3+4y^6\right)\)
\(=-\left(\dfrac{1}{2}x^2-2y^3\right)^2\)
g: =(4x)^3+1^3
=(4x+1)(16x^2-4x+1)
k: =x^3(27x^3-8)
=x^3(3x-2)(9x^2+6x+4)
l: =(x^3-y^3)(x^3+y^3)
=(x-y)(x+y)(x^2-xy+y^2)(x^2+xy+y^2)
1. \(x^3+2x^2-6x-27=\left(x-3\right)\left(x^2+5x+9\right)\)
2. \(9x^2+6x-4y^2-4y=\left(9x^2-4y^2\right)+\left(6x-4y\right)\)
\(=\left(3x-2y\right)\left(3x+2y\right)+2\left(3x-2y\right)=\left(3x-2y\right)\left(3x+2y+2\right)\)
3. \(12x^3+4x^2-27x-9=4x^2\left(3x+1\right)-9\left(3x+1\right)\)
\(=\left(3x+1\right)\left(x^2-\dfrac{9}{4}\right)=\left(x+\dfrac{1}{3}\right)\left(x+\dfrac{3}{2}\right)\left(x-\dfrac{3}{2}\right)\)
1) Ta có: \(x^3+2x^2-6x-27\)
\(=\left(x-3\right)\left(x^2+3x+9\right)+2x\left(x-3\right)\)
\(=\left(x-3\right)\left(x^2+5x+9\right)\)
2: Ta có: \(9x^2+6x-4y^2-4y\)
\(=\left(3x-2y\right)\left(3x+2y\right)+2\left(3x-2y\right)\)
\(=\left(3x-2y\right)\left(3x+2y+2\right)\)
c)
\(30ax-34bx-15a+17b\)
\(=(30ax-15a)-(34bx-17b)\)
\(=15a(2x-1)-17b(2x-1)\)
\(=(2x-1)(15a-17b)\)
d)
\(x^3-x^2y-x^2z-xyz\)
\(=x[x^2-xy-xz-yz]\)
a)
\(12x^3+4x^2-27x-9\)
\(=(12x^3+4x^2)-(27x+9)\)
\(=4x^2(3x+1)-9(3x+1)\)
\(=(3x+1)(4x^2-9)=(3x+1)[(2x)^2-3^2]\)
\(=(3x+1)(2x-3)(2x+3)\)
b)
\(x^6-x^4+2x^3+2x^2\)
\(=x^2(x^4-x^2+2x+2)\)
\(=x^2[x^2(x^2-1)+2(x+1)]\)
\(=x^2[x^2(x-1)(x+1)+2(x+1)]\)
\(=x^2(x+1)[x^2(x-1)+2]\)
\(=x^2(x+1)[(x^3+1)-(x^2-1)]\)
\(=x^2(x+1)[(x+1)(x^2-x+1)-(x-1)(x+1)]\)
\(=x^2(x+1)(x+1)(x^2-x+1-x+1)\)
\(=x^2(x+1)^2(x^2-2x+2)\)