bài 1:phân tích đa thức thành nhân tử :6x^3 +5x^2+6x-8
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Bài 1 :
\(x^2-6x+8=x^2-2x-4x+8=x\left(x-2\right)-4\left(x-2\right)=\left(x-4\right)\left(x-2\right)\)
Bài 2 :
\(x^8+x^7+1=x^8+x^7+x^6+x^5+x^4+x^3+x^2+x+1-x^6-x^5-x^4-x^3-x^2-x\)
\(=x^6\left(x^2+x+1\right)+x^3\left(x^2+x+1\right)+x^2+x+1-x^4\left(x^2+x+1\right)-x\left(x^2+x+1\right)\)
=\(\left(x^2+x+1\right)\left(x^6+x^3+1-x^4-x\right)\)
Tick đúng nha
a: \(12x^3-6x^2+3x\)
\(=3x\cdot4x^2-3x\cdot2x+3x\cdot1\)
\(=3x\left(4x^2-2x+1\right)\)
b: \(\dfrac{2}{5}x^2+5x^3+x^2y\)
\(=x^2\cdot\dfrac{2}{5}+x^2\cdot5x+x^2\cdot y\)
\(=x^2\left(\dfrac{2}{5}+5x+y\right)\)
c: \(14x^2y-21xy^2+28x^2y^2\)
\(=7xy\cdot2x-7xy\cdot3y+7xy\cdot4xy\)
\(=7xy\left(2x-3y+4xy\right)\)
a. \(5x^2-6x+1\)
=\(5x^2-x-5x+1\)
\(=\left(x-1\right)\left(5x-1\right)\)
a, Cách 1 : \(x^2+5x+6=x^2+2x+3x+6=\left(x+2\right)\left(x+3\right)\)
Cách 2 : \(x^2+5x+6=x^2+2.\frac{5}{2}x+\frac{25}{4}-\frac{25}{4}+6\)
\(=\left(x+\frac{5}{2}\right)^2-\frac{1}{4}=\left(x+2\right)\left(x+3\right)\)
b, Cách 1 : \(x^2-x-6=x^2+2x-3x-6=\left(x-3\right)\left(x+2\right)\)
Cách 2 : \(x^2-x-6=x^2-x+\frac{1}{4}-\frac{1}{4}-6=\left(x-\frac{1}{2}\right)^2-\frac{25}{4}=\left(x-3\right)\left(x+2\right)\)
c, Cách 1 : \(x^2+6x+8=x^2+4x+2x+8=\left(x+2\right)\left(x+4\right)\)
Cách 2 : \(x^2+6x+8=x^2+6x+9-1=\left(x+3\right)^2-1=\left(x+2\right)\left(x+4\right)\)
d, Cách 1 : \(x^2-2x-8=x^2+2x-4x-8=\left(x-4\right)\left(x+2\right)\)
Cách 2 : \(x^2-2x-8=x^2-2x+1-9=\left(x-1\right)^2-9=\left(x-4\right)\left(x+2\right)\)
1.
= (x^3 + 125 ) -(x^2 +5x)
=(x +5) (x^2 -5x +25) -x(x+5)
=(x+5)(x^2 -5x +25 -x)
=(x+5)(x^2 -6x +25)
2.
= (x^3 -27) + (2x^2 -6x)
=(x-3) (x^2 +3x +9) +2x (x-3)
=(x-3) (x^2 +3x +9 +2x)
=(x-3) (x^2 +5x +9)
6x3+5x2+6x-8
= 6x3-4x2+9x2-6x+12x-8
=2x2.(3x-2)+3x.(3x-2)+4.(3x-2)
=(3x-2)(2x2+3x+4)
a) x2 + 6x + 9 = x2 + 2 . x . 3 + 32 = (x + 3)2
b) 10x – 25 – x2 = -(-10x + 25 +x2) = -(25 – 10x + x2)
= -(52 – 2 . 5 . x – x2) = -(5 – x)2
c) 8x3 - 1/8 = (2x)3 – (1/2)3 = (2x - 1/2)[(2x)2 + 2x . 12 + (1/2)2]
= (2x - 1/2)(4x2 + x + 1/4)
d)1/25x2 – 64y2 = (1/5x)2(1/5x)2- (8y)2 = (1/5x + 8y)(1/5x - 8y)