1 Phân tích đa thức sau thành phân tử:
a) 3x^2-6x ; b) 18x^2-4x+12
c) 4x^2(2x-y)-12x(2x-y) ; d) 7(x-3y)-2x(3y-x) ; f) 6(x-2y)-3(2y-x)
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a) \(A=x^2-6x+9-9y^2\)
\(=\left(x-3\right)^2-\left(3y\right)^2\)
\(=\left(x-3-3y\right)\left(x-3+3y\right)\)
b) \(B=x^3-3x^2+3x-1+2\left(x^2-1\right)\)
\(=\left(x-1\right)^3+\left(2x+2\right)\left(x-1\right)\)
\(=\left(x-1\right)\left[\left(x-1\right)^2+2x+2\right]\)
\(=\left(x-1\right).\left(x^2+3\right)\)
a, \(A=\left(x-3\right)^2-9y^2=\left(x-3-3y\right)\left(x-3+3y\right)\)
b, \(B=\left(x-1\right)^3+2\left(x-1\right)\left(x+1\right)=\left(x-1\right)\left[\left(x-1\right)^2+2\left(x+1\right)\right]\)
\(=\left(x-1\right)\left(x^2-2x+1+2x+2\right)=\left(x-1\right)\left(x^2+3\right)\)
\(x^3-3x^2+6x-4\)
\(=x^3-2x^2+4x-x^2+2x-4\)
\(=\left(x^3-2x^2+4x\right)-\left(x^2-2x+4\right)\)
\(=x\left(x^2-2x+4\right)-\left(x^2-2x+4\right)\)
\(=\left(x-1\right)\left(x^2-2x+4\right)\)
x^3 - 3x^2 + 6x - 4
<=> x^3-3x^2+3x-1+3x-3
<=>(x-1)^3+3(x-1)
<=>(x-1)+((x-1)^2+3)
<=>(x-1)+(x^2-2x+4)
a) 3x^2 -6x + 3 - 3y^2
=3.(x2-2x+1-y2)
=3.[(x-1)2-y2]
=3.(x-1+y)(x-1-y)
3x3 + 6x2 + 3x - 12xy2
= 3x(x2 + 2x + 1 - 4y2)
= 3x[(x + 1)2 - (2y)2]
= 3x(x + 1 + 2y)(x - 2y + 1)
\(3x^3+6x^2+3x-12xy^2\)
\(=3x\left(x^2+2x+1-4y^2\right)\)
\(=3x\left[\left(x+1\right)^2-\left(2y\right)^2\right]\)
\(=3x\left(x+1-2y\right)\left(x+1+2y\right)\)
a ) x=0; x = -(căn bậc hai(7)*i-3)/8;x = (căn bậc hai(7)*i+3)/8;
b ) -(y-x-3)*(y+x+3)
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: \(14x^2y-21xy^2+28x^2y^2\)
\(=7xy\cdot2x-7xy\cdot3y+7xy\cdot4xy\)
\(=7xy\left(2x-3y+4xy\right)\)
\(3x^2-6x+9x^2=12x^2-6x=6x\left(2x-1\right)\)
\(a,3x^2-6x\)
\(=3x\left(x-2\right)\)
\(b,18x^2-4x+12\)
\(=2\left(9x^2-2x+6\right)\)
\(c,4x^2\left(2x-y\right)-12x\left(2x-y\right)\)
\(=\left(2x-y\right)\left(4x^2-12x\right)\)
\(=4x\left(2x-y\right)\left(x-3\right)\)
\(d,7\left(x-3y\right)-2y\left(3y-x\right)\)
\(=7\left(x-3y\right)+2y\left(x-3y\right)\)
\(=\left(x-3y\right)\left(2y+7\right)\)
\(f,6\left(x-2y\right)-3\left(2y-x\right)\)
\(=6\left(x-2y\right)+3\left(x-2y\right)\)
\(=\left(x-2y\right)\left(6+3\right)=9\left(x-2y\right)\)