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\(x^6-x^4-9x^3+9x^2\)
\(\left(x^6-x^4\right)-\left(9x^3-9x^2\right)\)
\(x^4\left(x^2-x\right)-9x\left(x^2-x\right)\)
\(\left(x^2-x\right)\left(x^4-9x\right)\)
\(x^3-9x^2+14x\)
= \(x^3-7x^2-2x^2+14x\)
= \(x^2.\left(x-7\right)-2x.\left(x-7\right)\)
= \(\left(x-7\right).\left(x^2-2x\right)\)
= \(\left(x-7\right).\left(x-2\right).x\)
\(x^3-9x^2+14x\)
\(=x\left(x^2-9x+14\right)\)
\(=x\left(x^2-7x-2x+14\right)\)
\(=x\left[x\left(x-7\right)-2\left(x-7\right)\right]\)
\(=x\left(x-2\right)\left(x-7\right)\)
x^3 -9x^2 +6x +16
<=>x3 - 8x2 - x2 + 8x - 2x + 16
<=>x2(x -8) - x(x - 8) - 2(x - 8)
<=>(x - 8)(x2 - x - 2)
<=> (x - 8)(x + 1)(x - 2)
= (x^6 - x^4) - (9x^3 - 9x^2)
= x^4 (x^2 +1) - 9x^2 (x - 1)
= x^4 (x + 1) (x - 1) - 9x^2 (x - 1)
= (x - 1) {x^4 (x + 1) - 9x^2}
= (x - 1) (x^5 + x^4 - 9x^2)
= (x -1) {x^2 (x^3 + x^2 - 9)}
x6 - x 4- 9x3 + 9x2
= (x6 - x 4) - (9x3 - 9x2)
= x4 (x2 - 1) - 9x2 (x - 1)
= x4 (x-1) (x+1) - 9x2 (x - 1)
= x2 (x-1) (x2 (x+1) - 9)
= x2 (x-1) (x3 + x2 - 9)
x3 + 2x2y + xy2 - 9x
= x( x2 + 2xy + y2 - 9 )
= x[ ( x2 + 2xy + y2 ) - 9 ]
= x[ ( x + y )2 - 32 ]
= x( x + y - 3 )( x + y + 3 )
Bài làm
\(x^3+2x^2y+xy^2-9x=x\left(x^2+2xy+y^2-9\right)\)
\(=x\left[\left(x+y\right)^2-9\right]=x\left(x+y-3\right)\left(x+y+3\right)\)
\(27+27x+9x^2+x^3\)
\(=x^3+9x^2+27x+27\)
\(=x^3+3x^2+6x^2+18x+9x+27\)
\(=x^2\left(x+3\right)+6x\left(x+3\right)+9\left(x+3\right)\)
\(=\left(x+3\right)\left(x^2+6x+9\right)\)
\(=\left(x+3\right)\left(x+3\right)^2=\left(x+3\right)^3\)
Nếu nhìn kĩ thì bạn sẽ thấy đây là hằng đẳng thức nhé !
\(x^3+9x^2+27x+27=x^3+3.3.x^2+3.3^2.x+3^3\)
\(=\left(x+3\right)^3\)
9x-x^3
=x(9-x^2)
=x(3-x)(3+x)