Phân tích đa thức thành nhân tử:
x10+x2+1
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Câu 1:
$x^2+4y^2+4xy-16=[x^2+(2y)^2+2.x.2y]-16$
$=(x+2y)^2-4^2=(x+2y-4)(x+2y+4)$
Câu 2:
$x^3+x^2+y^3+xy=(x^3+y^3)+(x^2+xy)$
$=(x+y)(x^2-xy+y^2)+x(x+y)=(x+y)(x^2-xy+y^2+x)$
Câu 1:
\(x^2+4y^2+4xy-16\)
\(=\left(x+2y\right)^2-16\)
\(=\left(x+2y+4\right)\left(x+2y-4\right)\)
Câu 2:
\(x^3+x^2+y^3+xy\)
\(=\left(x^3+y^3\right)\left(x^2+xy\right)\)
\(=\left(x+y\right)\left(x^2-xy+y^2\right)+x\left(x+y\right)\)
\(=\left(x+y\right)\left(x^2-xy+y^2+x\right)\)
\(\left(x^2+x+1\right)\left(x^2+x+5\right)-21=x^4+x^3+5x^2+x^3+x^2+5x+x^2+x+5-21=x^4+2x^3+7x^2+6x-16=\left(x-1\right)\left(x+2\right)\left(x^2+x+8\right)\)
\(=\left(x^2+x+1\right)\left(x^2+x+1+4\right)-21\)
\(=\left(x^2+x+1\right)^2+4\left(x^2+x+1\right)-21\)
\(=\left(x^2+x+1\right)^2-3\left(x^2+x+1\right)+7\left(x^2+x+1\right)-21\)
\(=\left(x^2+x+1\right)\left(x^2+x-2\right)+7\left(x^2+x-2\right)\)
\(=\left(x^2+x-2\right)\left(x^2+x+8\right)\)
\(=\left(x-1\right)\left(x-2\right)\left(x^2+x+8\right)\)
\(x^2+2x+1-16=\left(x+1\right)^2-4^2=\left(x+1-4\right).\left(x+1+4\right)=\left(x-3\right).\left(x+5\right)\)
\(x^2+2x+1-16=\left(x^2+2x+1\right)-4^2=\left(x+1\right)^2-4^2=\left(x+1-4\right)\left(x+1+4\right)=\left(x-3\right)\left(x+5\right)\)
-Đặt \(t=\left(x^2-x+1\right)\)
\(\left(x^2-x+1\right)^2-5x\left(x^2-x+1\right)+4x^2\)
\(=t^2-5xt+4x^2\)
\(=t^2-4xt-xt+4x^2\)
\(=t\left(t-4x\right)-x\left(t-4x\right)\)
\(=\left(t-4x\right)\left(t-x\right)\)
\(=\left(x^2-x+1-4x\right)\left(x^2-x+1-x\right)\)
\(=\left(x^2-5x+1\right)\left(x^2-2x +1\right)\)
\(=\left(x^2-5x+1\right)\left(x-1\right)^2\)
1: \(-x^2+2x+8\)
\(=-\left(x^2-2x-8\right)\)
\(=-\left(x-4\right)\left(x+2\right)\)
2: \(2x^2-3x+1=\left(x-1\right)\left(2x-1\right)\)
`x^2+2x+1-y^2+2y-1`
`=(x^2+2x+1)-(y^2-2y+1)`
`=(x+1)^2-(y-1)^2`
`=(x+1+y-1)(x+1-y+1)`
`=(x+y)(x-y+2)`
Ta có: \(x^2+2x+1-y^2+2y-1\)
\(=\left(x+1\right)^2-\left(y-1\right)^2\)
\(=\left(x+1-y+1\right)\left(x+1+y-1\right)\)
\(=\left(x-y+2\right)\left(x+y\right)\)
\(x^{10}+x^2+1\)
\(=x^{10}+x^8-x^8+x^6-x^6+x^4-x^4+x^2+1\)
\(=\left(x^{10}+x^8+x^6\right)-\left(x^8+x^6+x^4\right)+\left(x^4+x^2+1\right)\)
\(=x^6\left(x^4+x^2+1\right)-x^4\left(x^4+x^2+1\right)+\left(x^4+x^2+1\right)\)
\(=\left(x^6-x^4+1\right)\left(x^4+x^2+1\right)\)
\(=\left(x^6-x^4+1\right)\left(x^4+x^3-x^3+x^2+x^2-x^2+x-x+1\right)\)
\(=\left(x^6-x^4+1\right)\)
\(\left[\left(x^4-x^3+x^2\right)+\left(x^3-x^2+x\right)+\left(x^2-x+1\right)\right]\)
\(=\left(x^6-x^4+1\right)\)
\(\left[x^2\left(x^2-x+1\right)+x\left(x^2-x+1\right)+\left(x^2-x+1\right)\right]\)
\(=\left(x^6-x^4+1\right)\left(x^2+x+1\right)\left(x^2-x+1\right)\)
x10+x2+1
=( x10 - x ) + ( x2 + x + 1)
= x[ (x3)3-1] + ( x2 + x +1)
=x[( x3-1)( x6 + x3 +1) + (x2 + x +1)
=x[(x-1)(x2 + x +1)( x6 + x3 +1)] + (x2 + x +1)
=x(x2 + x +1)[(x-1)( x6 + x3 +1) +1 ]
=x2(x2 + x +1)(x6-x5+x3-x2+1)