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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)
a)\(3x^2-8x+4\)
\(=3x^2-2x-6x+4\)
\(=x\left(3x-2\right)-2\left(3x-2\right)\)
\(=\left(x-2\right)\left(3x-2\right)\)
b)\(4x^4+81\)
\(=4x^4+36x^2+81-36x^2\)
\(=\left(2x^2+9\right)^2-36x^2\)
\(=\left(2x^2-6x+9\right)\left(2x^2+6x+9\right)\)
c)\(x^8+98x^4+1\)
\(=\left(x^8+2x^4+1\right)+96x^4\)
\(=\left(x^4+1\right)^2+16x^2\left(x^4+1\right)+64x^4-16x^2\left(x^4+1\right)+32x^4\)
\(=\left(x^4+8x^2+1\right)^2-16x^2\left(x^4-2x^2+1\right)\)
\(=\left(x^4+8x^2+1\right)^2-16x^2\left(x^4-2x^2+1\right)\)
\(=\left(x^4+8x^2+1\right)^2-\left(4x^3-4x\right)^2\)
\(=\left(x^4+4x^3+8x^2-4x+1\right)\left(x^4-4x^3+8x^2+4x+1\right)\)
d)\(x^4+6x^3+7x^2-6x+1\)
\(=x^4+3x^3-x^2+3x^3+9x^2-3x-x^2-3x+1\)
\(=x^2\left(x^2+3x-1\right)+3x\left(x^2+3x-1\right)-\left(x^2+3x-1\right)\)
\(=\left(x^2+3x-1\right)\left(x^2+3x-1\right)\)\(=\left(x^2+3x-1\right)^2\)
1, x^2 +5x+4x+20
= x(x+4)+5(x+4)
= (x+5).(x+4)
2,x^2 -x -20
= x^2 -5x+4x-20
= x(x-5)+4(x-5)
=(x+4).(x-5)
3,3x^2 +3x -2x -2
= 3x(x+1)-2(x+1)
= (3x-2)(x+1)
4, 2x^2-4x-x-2
=2x(x-2)-x-2
=(2x-1)(x+2)
5,6x^2-2x+9x-3
=2x(3x-1)+3(3x-1)
=(2x+3)(3x-1)
6,3x^2 +2x+9x+6
=3x(x+3)+2(x+3)
=(3x+2)(x+3)
7,= 2(x^2-10x+3)
8,=x^4 +4^3
mk làm luôn ko chép đề nha bn
a)\(x^3+x+2=x^3+1+x+1\)
\(=\left(x+1\right)\left(x^2-x+1\right)+\left(x+1\right)\)
\(=\left(x+1\right)\left(x^2-x+2\right)\)
b)\(x^3+3x^2-4=x^3-1+3x^2-3\)
\(=\left(x-1\right)\left(x^2+x+1\right)+3\left(x^2-1\right)\)
\(=\left(x-1\right)\left(x^2+x+1\right)+3\left(x-1\right)\left(x+1\right)\)
\(=\left(x-1\right)\left[x^2+x+1+3x+3\right]\)
\(=\left(x-1\right)\left(x+2\right)^2\)
a/
\(=x^4-x^3-x^2+3x+\left(2x^3-2x^2-2x+6\right)\)
\(=x\left(x^3-x^2-x+3\right)+2\left(x^3-x^2-x+3\right)\)
\(=\left(x+2\right)\left(x^3-x^2-x+3\right)\)
b/
\(=x^4+x^3+5x^2+\left(x^2+x+5\right)\)
\(=x^2\left(x^2+x+5\right)+\left(x^2+x+5\right)\)
\(=\left(x^2+1\right)\left(x^2+x+5\right)\)
c giống b
d/ \(=x^4-2x^3+7x^2+\left(x^3-2x^2+7x\right)+\left(2x^2-4x+14\right)\)
\(=x^2\left(x^2-2x+7\right)+x\left(x^2-2x+7\right)+2\left(x^2-2x+7\right)\)
\(=\left(x^2+x+2\right)\left(x^2-2x+7\right)\)