Phân tích đa thức thành nhân tử
\(x^4+5x^3+10x-4\)
b ) \(x^2-2xy+y^2+3x-3y\)
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\(5x^4y+10x^3y+10x^2y^3+5xy^4\)
\(=5xy.x^3+5xy.2x^3+5xy.2xy^3+5xy.y^3\)
\(=5xy\left(x^3+2x^3+2xy^3+y^3\right)\)
Ht pt
x2-2xy+y2+3x-3y-10
= (x-y)2+3(x-y)-10
= [(x-y)2+5(x-y)]-[2(x-y)+10]
= (x-y)(x-y+5)-2(x-y+5)
= (x-y+5)(x-y-2)
Ta có: \(x^2-2xy+y^2+3x-3y-10\)
\(=\left(x-y\right)^2+3\left(x-y\right)-10\)
\(=\left(x-y+5\right)\left(x-y-2\right)\)
\(x^2-2xy+x-2y=x\left(x-2y\right)+x-2y=\left(x-2y\right)\left(x+1\right)\)
\(3x^3+6x+3-3y^2=3\left[\left(x^2+2x+1\right)-y^2\right]=3\left[\left(x+1\right)^2-y^2\right]=3\left(x-y+1\right)\left(x+y+1\right)\)
\(5x^2-4\left(x^2-2x+1\right)-5=\left(5x^2-5\right)-4\left(x-1\right)^2=5\left(x^2-1\right)-4\left(x-1\right)^2=5\left(x-1\right)\left(x+1\right)-4\left(x-1\right)^2=\left(x-1\right)\left[5\left(x+1\right)-4\left(x-1\right)\right]=\left(x-1\right)\left(5x+5-4x+4\right)=\left(x-1\right)\left(x+9\right)\)
a) x2+x-2
= x2-x+2x-2
= x(x-1)+2(x-1)
= (x+2)(x-1)
b) 2x2+5x+3
= 2x2+2x+3x+3
= 2x(x+1)+3(x+1)
= (2x+3)(x+1)
c) 3x2+5x-2
= 3x2+6x-1x-2
= 3x(x+2)-1(x+2)
= (3x-1)(x+2)
1) \(x^4-3x^2-x+3\)
\(=x\left(x^3-1\right)-3\left(x^2-1\right)\)
\(=x\left(x-1\right)\left(x^2+x+1\right)-3\left(x+1\right)\left(x-1\right)\)
\(=\left(x-1\right)\left(x^3+x^2+x-3x-3\right)\)
\(=\left(x-1\right)\left(x^3+x^2-2x-3\right)\)
2) \(3x+3y-x^2-2xy-y^2\)
\(=3\left(x+y\right)-\left(x^2+2xy+y^2\right)\)
\(=3\left(x+y\right)-\left(x+y\right)^2\)
\(=\left(x+y\right)\left(3-x-y\right)\)
3) \(x^4-x\)
\(=x\left(x^3-1\right)\)
\(=x\left(x-1\right)\left(x^2+x+1\right)\)
4) \(x^2+5x+4\)
\(=x^2+x+4x+4\)
\(=x\left(x+1\right)+4\left(x+1\right)\)
\(=\left(x+1\right)\left(x+4\right)\)
5) \(4x^2+4x-8\)
\(=4\left(x^2+x-2\right)\)
\(=4\left(x^2-x+2x-2\right)\)
\(=4\left[x\left(x-1\right)+2\left(x-1\right)\right]\)
\(=4\left(x-1\right)\left(x+2\right)\)
6) \(x^2+x-42\)
\(=x^2-6x+7x-42\)
\(=x\left(x-6\right)+7\left(x-6\right)\)
\(=\left(x-6\right)\left(x+7\right)\)
Ta có: \(\left(4x+1\right)\left(12x-1\right)\left(3x+2\right)\left(x+1\right)-4\)
\(=\left(12x^2+8x+3x+2\right)\left(12x^2+12x-x-1\right)-4\)
\(=\left(12x^2+11x+2\right)\left(12x^2+11x-1\right)-4\)
\(=\left(12x^2+11x\right)^2+\left(12x^2+11x\right)-6\)
\(=\left(12x^2+11x+3\right)\left(12x^2+11x-2\right)\)
a: \(=5xy\left(x^2-2xy+y^2\right)=5xy\left(x-y\right)^2\)
b: \(=2x^2+10x-3x-15\)
\(=2x\left(x+5\right)-3\left(x+5\right)=\left(x+5\right)\left(2x-3\right)\)