Phân tích đa thức thành nhân tử :
\(x^3+3xy+y^3-1\)
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\(=\left(x+y\right)^3-\left(x+y\right)=\left(x+y\right)\left[\left(x+y\right)^2-1\right]\\ =\left(x+y\right)\left(x+y+1\right)\left(x+y-1\right)\)
\(x^3+y^3-3x^2+3x-1\\=(x^3-3x^2+3x-1)+y^3\\=(x-1)^3+y^3\\=(x-1+y)[(x-1)^2-(x-1)y+y^2]\\=(x+y-1)(x^2-2x+1-xy+y+y^2)\)
\(1,=x\left(x^2-2x+1-y^2\right)=x\left[\left(x-1\right)^2-y^2\right]=x\left(x-y-1\right)\left(x+y-1\right)\\ 2,=\left(x+y\right)^3\\ 3,=\left(2y-z\right)\left(4x+7y\right)\\ 4,=\left(x+2\right)^2\\ 5,Sửa:x\left(x-2\right)-x+2=0\\ \Leftrightarrow\left(x-2\right)\left(x-1\right)=0\Leftrightarrow\left[{}\begin{matrix}x=1\\x=2\end{matrix}\right.\)
x3 - x + 3x2y + 3xy2 + y3 - y ( sửa -x3 -> x3 )
= ( x3 + 3x2y + 3xy2 + y3 ) - ( x + y )
= ( x + y )3 - ( x + y )
= ( x + y )[ ( x + y )2 - 1 ]
= ( x + y )( x + y - 1 )( x + y + 1 )
`#3107`
`x^4 - 8x + 63`
`= x^4 + 4x^3 + 9x^2 - 4x^3 -16x^2 - 36x + 7x^2 + 28x + 63`
`= (x^4 + 4x^3 + 9x^2) - (4x^3 + 16x^2 + 36x) + (7x^2 + 28x + 63)`
`= x^2(x^2 + 4x + 9) - 4x(x^2 + 4x + 9) + 7(x^2 + 4x + 9)`
`= (x^2 + 4x + 9)(x^2 - 4x + 7)`
____
`64x^4 + y^4`
`= 64x^4 + 16x^2y^2 + y^4 - 16x^2y^2`
`= (64x^4 + 16x^2y^2 + y^4) - (16x^2y^2)`
`= [(8x^2)^2 + 2*8x^2*y^2 + (y^2)^2] - (4xy)^2`
`= (8x^2 + y^2)^2 - (4xy)^2`
`= (8x^2 + y^2 - 4xy)(8x^2 + y^2 + 4xy)`
____
`x^3 + 3xy`
`= x(x^2 + 3y)`
Thêm bớt hạng tử thôi:
\(x^3+3xy+y^3-1\)
\(=\left(x^3+3x^2y+3xy^2+y^3-1\right)-3x^2y-3xy^2+3xy\)
\(=\left[\left(x+y\right)^3-1^3\right]-3xy\left(x+y-1\right)\)
\(=\left(x+y-1\right)\left[\left(x+y\right)^2+x+y+1\right]-3xy\left(x+y-1\right)\)
\(=\left(x+y-1\right)\left(x^2+2xy+y^2+x+y+1-3xy\right)\)
\(=\left(x+y-1\right)\left(x^2-xy+y^2+x+y+1\right)\)
Có phải đề như thế này không bạn
\(x^3+3xy+y^3-1\)
\(=\left(x+y\right)^3-1+3xy-3xy\left(x+y\right)\)
\(=\left(x+y-1\right)\left(x^2+y^2+2xy+x+y+1\right)-3xy\left(x+y-1\right)\)
\(=\left(x+y-1\right)\left(x^2+y^2+2xy+x+y+1-3xy\right)\)
\(=\left(x+y-1\right)\left(x^2+y^2-xy+x+y+1\right)\)
\(x^3+3xy+y^3-1=\left(x^3+y^3\right)+\left(x^2+2xy+y^2-1\right)-\left(x^2-xy+y^2\right)\)
\(=\left(x+y\right)\left(x^2-xy+y^2\right)+\left(x+y-1\right)\left(x+y+1\right)-\left(x^2-xy+y^2\right)\)
\(=\left(x^2-xy+y^2\right)\left(x+y-1\right)+\left(x+y-1\right)\left(x+y+1\right)\)
\(=\left(x+y-1\right)\left(x^2-xy+y^2+x+y+1\right)\)
\(x^3+3xy+y^3-1\)
\(=\left(x+y\right)^3-1-3x^2y-3xy^2+3xy\)
\(=\left(x+y-1\right)\left[\left(x+y\right)^2+x+y+1\right]-3xy\left(x+y-1\right)\)
\(=\left(x+y-1\right)\left(x^2+y^2+2xy+x+y+1-3xy\right)\)
\(=\left(x+y-1\right)\left(x^2+y^2-xy+x+y+1\right)\)