Phân tích đa thức thành nhân tử:
x^5-x^4-1
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\(x^4-x^2+2x+2\)
\(=x^4-2x^3+2x^2+2x^3-4x^2+4x+x^2-2x+2\)
\(=\left(x^4-2x^3+2x^2\right)+\left(2x^3-4x^2+4x\right)+\left(x^2-2x+2\right)\)
\(=x^2\left(x^2-2x+2\right)+2x\left(x^2-2x+2\right)+\left(x^2-2x+2\right)\)
\(=\left(x^2-2x+2\right)\left(x^2+2x+1\right)\)
\(=\left(x^2-2x+2\right)\left(x+1\right)^2\)
=x11-x2+x2+x+1
=x2(x9-1)+(x2+x+1)
=x2[(x3)3-13)+(x2+x+1)
=x2(x3-1)(x6+x3+1)+(x2+x+1)
=x2(x6+x3+1)(x-1)(x2+x+1)+(x2+x+1)
Đặt nhân tử chung là x2+x+1 rồi phá hết ngoặc là xong
\(x^8+3x^3+1\)
\(=x^8-x^4+4x^4+4\)
\(=\left(x^4-1\right)\cdot\left(x^4+1\right)+4\cdot\left(x^4+1\right)\)
\(=\left(x^4+1\right)\cdot\left(x^4-1+4\right)\)
\(=\left(x^4+1\right)\cdot\left(x^4+3\right)\)
\(x^8+x+1\)
\(=\left(x^8-x^5\right)+\left(x^5-x^2\right)+\left(x^2+x+1\right)\)
\(x^5\left(x^3-1\right)+x^2\left(x^3-1\right)+\left(x^2+x+1\right)\)
\(=x^5\left(x-1\right)\left(x^2+x+1\right)+x^2\left(x-1\right)\left(x^2+x+1\right)+\left(x^2+x+1\right)\)
\(=\left(x^6-x^5\right)\left(x^2+x+1\right)+\left(x^3-x^2\right)\left(x^2+x+1\right)+\left(x^2+x+1\right)\)
\(=\left(x^2+x+1\right)\left(x^6-x^5+x^3-x^2+1\right)\)
x^4+64
=(x^2)^2+8^2+2.x^2.8-2.x^2.8
=(x^2+8)^2-16x^2
=(x^2+8-4x)(x^2+8+4x)
\(x^3+27x+\left(x+3\right)\left(x-9\right)\)
⇒\(x^3+27x+x^2-6x-27\)
⇒\(x^3+x^2+21x-27\)
Chịu
x^5 - x^4 - 1
= x^5 - x^3 - x² - x^4 + x² + x + x^3 - x - 1
= x²( x^3 - x - 1 ) - x( x^3 - x - 1 ) + ( x^3 - x - 1 )
= ( x² - x + 1)( x^3 - x - 1 )
x5-x4-1=x5-x4+x3-x3-1=x3(x2-x+1)-(x3+1)=x3(x2-x+1)-(x+1)(x2-x+1)=(x3-1)(x2-x+1)=(x-1)(x2+x+1)(x2-x+1)