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x^4+x^2+1 = (x^4+2x^2+1)-x^2 = (x^2+1)^2-x^2 = (x^2-x+1).(x^2+x+1)
k mk nha
x5-x4-1=x5-x3-x2-x4+x2+x+x3-x-1
=x2.(x3-x-1)-x.(x3-x-1)+(x3-x-1)
=(x3-x-1)(x2-x+1)
x^4+x^2+1 = (x^4+2x^2+1)-x^2 = (x^2+1)^2-x^2 = (x^2-x+1).(x^2+x+1)
k mk nha
x5 + x4 + 1
= x5 - x3 - x2 - x4 + x2 + x + x3 - x - 1
= x2 ( x3 - x - 1) - x ( x3 - x - 1) + 1 ( x3 - x - 1)
= ( x3 - x - 1) ( x2 - x + 1 )
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)
(x-1)(x-2)(x+4)(x+5)-72=[(x-1)(x+4)][x-2)(x+5)]-72=(x^2+3x-4)(x^2+3x-10)-72
Đặt x^2+3x-4=t nên x^2+3x-10=t-6. Thay vào (*) ta được :
(x-1)(x-2)(x+4)(x+5)=t.(t-6)-72=t^2-6t-72=t^2-6t+9-81=(t-3)^2-9^2=(t-3-9)(t-3+9)=(t-12)(t+6)=(x^2+3x-16)(x^2+3x+2)
Ta có: \(\left(x-2\right)\left(x-3\right)\left(x-4\right)\left(x-5\right)+1\)
\(=\left[\left(x-2\right)\left(x-5\right)\right]\cdot\left[\left(x-3\right)\left(x-4\right)\right]+1\)
\(=\left(x^2-7x+10\right)\cdot\left(x^2-7x+12\right)+1\)
\(=\left[\left(x^2-7x+11\right)-1\right]\cdot\left[\left(x^2-7x+11\right)+1\right]\)
\(=\left(x^2-7x+11\right)^2-1+1\)
\(=\left(x^2-7x+11\right)^2\)
\(\left(x-2\right)\left(x-3\right)\left(x-4\right)\left(x-5\right)+1\)
\(=\left(x-2\right)\left(x-5\right)\left(x-4\right)\left(x-3\right)+1\)
\(=\left(x^2-7x+10\right)\left(x^2-7x+12\right)+1\)
Đặt t = \(x^2-7x\)
\(t\left(t+2\right)+1\)
\(=t^2+2t+1\)
\(=\left(t+1\right)^2\)
\(=\left(x^2-7x+1\right)^2\)
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 )
tích nha nha nha
\(x^5+x^4+1\)
\(=\left(x^5-x^2\right)+\left(x^4-x\right)+\left(x^2+x+1\right)\)
\(=x^2\left(x^3-1\right)+x\left(x^3-1\right)+\left(x^2+x+1\right)\)
\(=\left(x^3-1\right)\left(x^2+x\right)+\left(x^2+x+1\right)\)
\(=\left(x-1\right)\left(x^2+x+1\right)\left(x^2+x\right)+\left(x^2+x+1\right)\)
\(=\left(x^2+x+1\right)\left(x^3-x+1\right)\)
\(\left(x+1\right)\left(x+5\right)\left(x+2\right)\left(x+4\right)-4\)
\(=\left(x^2+6x+5\right)\left(x^2+6x+8\right)-4\)
Đặt \(x^2+6x+5=t\)
\(\Rightarrow\left(x+1\right)\left(x+5\right)\left(x+2\right)\left(x+4\right)-4\)
\(=t\left(t+3\right)-4\)
\(=t^2+3t-4\)
\(=\left(t^2-t\right)+\left(4t-4\right)\)
\(=t.\left(t-1\right)+4\left(t-1\right)\)
\(=\left(t-1\right)\left(t+4\right)\)
\(=\left(x^2+6x+4\right)\left(x^2+6x+9\right)\)
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 )