Phân tích thành nhân tử ( bằng kĩ thuật tách hạng tử ) :
6x^2 + 12x + 6
8x^2 - 2x - 3
8x^2 + 2x - 3
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a. \(=6x^2-4x-9x+6=2x\left(3x-2\right)-3\left(3x-2\right)=\left(3x-2\right)\left(2x-3\right)\)
b. \(=6x^2+4x+9x+6=2x\left(3x+2\right)+3\left(3x+2\right)=\left(3x+2\right)\left(2x+3\right)\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a. = \(6x^2+3x+12x+6=3x\left(2x+1\right)+6\left(2x+1\right)=\left(2x+1\right)\left(3x+6\right)=3\left(2x+1\right)\left(x+2\right)\)
b. \(=6x^2-3x-12x+6=3x\left(2x-1\right)-6\left(2x-1\right)=3\left(2x-1\right)\left(x-2\right)\)
c. \(=6x^2+2x+18x+6=2x\left(3x+1\right)+6\left(3x+1\right)=\left(2x+6\right)\left(3x+1\right)=2\left(x+3\right)\left(3x+1\right)\)
d. \(=6x^2-2x-18x+6=2x\left(3x-1\right)-6\left(3x-1\right)=2\left(x-3\right)\left(3x-1\right)\)
(+) 6x^2 + 15x + 6 = 6x^2 + 12x + 3x + 6
= 6x ( x+ 2 ) + 3 ( x + 2)
= ( 6x + 3) ( x + 2 )
= 3 (2 x + 1 ) ( x + 2)
(+) 6x^2 - 15x + 6 = 6x^2 - 3x - 12x + 6
= 3x( 2x - 1 ) - 6 ( 2x - 1 )
= ( 3 x - 6 )( 2x - 1)
= 3 ( x- 2 ) (2x- 1)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(1,2x^2-3x-2\)
\(=2x^2-4x+x-2\)
\(=2x\left(x-2\right)+\left(x-2\right)\)
\(=\left(2x+1\right)\left(x-2\right)\)
\(2,4x^2-7x-2\)
\(=4x^2-8x+x-2\)
\(=4x\left(x-2\right)+x-2\)
\(\left(4x+1\right)\left(x-2\right)\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có: \(-8x^2+23x+3\)
\(=\left(-8x^2+24x\right)-\left(x-3\right)\)
\(=-8x\left(x-3\right)-\left(x-3\right)\)
\(=\left(-8x-1\right)\left(x-3\right)\)
\(=\left(3-x\right)\left(8x+1\right)\)
\(-8x^2+23x+3\)
\(=-\left(8x^2-23x-3\right)\)
\(=-\left(8x^2-24x+x-3\right)\)
\(=-\left[8x\left(x-3\right)+\left(x-3\right)\right]\)
\(=-\left(8x+1\right)\left(x-3\right)\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) -8x2+5x+3=-8x^2+8x-3x+3=-8x(x-1)-3(x-1)=-(8x+3)(x-1)
b)8x^2-10x-3=8x^2-12x+2x-3=8x(x-1,5)+2(x-1,5)=2(4x+1)(x-1,5)
c)=8x^2-2x+12x-3=2x(4x-1)+3(4x-1)=(2x+3)(4x-1)
d)=-8x^2+24x-x+3=-8x(x-3)-(x-3)=-(8x+1)(x-3)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(x^3+4x^2-21x\)
\(=x\left(x^2+4x-21\right)\)
\(=x\left(x^2-3x+7x-21\right)\)
\(=x\left[x\left(x-3\right)+7\left(x-3\right)\right]\)
\(=x\left(x-3\right)\left(x+7\right)\)
b) \(5x^3+6x^2+x\)
\(=x\left(5x^2+6x+1\right)\)
\(=x\left(5x^2+5x+x+1\right)\)
\(=x\left[5x\left(x+1\right)+\left(x+1\right)\right]\)
\(=x\left(x+1\right)\left(5x+1\right)\)
c) \(x^3-7x+6\)
\(=x^3+2x^2-3x-2x^2-4x+6\)
\(=x\left(x^2+2x-3\right)-2\left(x^2+2x-3\right)\)
\(=\left(x-2\right)\left(x^2+2x-3\right)\)
\(=\left(x-2\right)\left(x-1\right)\left(x+3\right)\)
d) \(3x^3+2x-5\)
\(=3x^3+3x^2+5x-3x^2-3x-5\)
\(=x\left(3x^2+3x+5\right)-\left(3x^2+3x+5\right)\)
\(=\left(x-1\right)\left(3x^2+3x+5\right)\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài làm:
Ta có: \(3x^2+3x-6\)
\(=\left(3x^2+6x\right)-\left(3x+6\right)\)
\(=3x\left(x+2\right)-3\left(x+2\right)\)
\(=3\left(x-1\right)\left(x+2\right)\)
\(3x^2+3x-6\)
\(=3\left(x^2+x-2\right)\)
\(=3\left(x^2+2x-x-2\right)\)
\(=3\left[x\left(x+2\right)-\left(x+2\right)\right]\)
\(=3\left(x-1\right)\left(x+2\right)\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(12x^2+7x-12=12x^2-5x+12x-12\)
\(=x\left(12x-5\right)+12\left(x-1\right)\)
Đề sai rồi bạn ời
a. \(=6.\left(x^2+2x+1\right)=6\left(x+1\right)^2\)
b. \(=8x^2-6x+4x-3=2x\left(4x-3\right)+\left(4x-3\right)=\left(2x+1\right)\left(4x-3\right)\)
c. \(=8x^2+6x-4x-3=2x\left(4x+3\right)-\left(4x+3\right)=\left(2x-1\right)\left(4x+3\right)\)