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\(3\left(x^4+x^2+1\right)-\left(x^2+x+1\right)^2=3[\left(x^4+2x^2+1\right)-x^2]-\left(x^2+x+1\right)^2\)\(=3[\left(x^2+1\right)^2-x^2]-\left(x^2+x+1\right)^2\)
\(=3\left(x^2-x+1\right)\left(x^2+x+1\right)-\left(x^2+x+1\right)^2\)
\(=\left(x^2+x+1\right)\left(2x^2-4x+2\right)=2\left(x-1\right)^2\left(x^2+x+1\right)\)
x8 + x7 +1=x8+x7+x6+x5+x4+x3+x2+x+1-x6-x5-x4-x3-x2-x
=x6(x2+x+1)+x3(x2+x+1)+(x2+x+1)-x4(x2+x+1)-x(x2+x+1)
=(x2+x+1)(x6+x3-x4-x)
=(x2+x+1)[x3(x3+1)-x(x3+1)]
=(x2+x+1)(x3+1)(x3-x)
=x(x2+x+1)(x+1)(x2-x+1)(x2-1)
=x(x2+x+1)(x+1)(x2-x+1)(x+1)(x-1)
=x(x2+x+1)(x+1)2(x2-x+1)(x-1)
\(\left(x+1\right)^4+\left(x^2+x+1\right)^2\)
\(=\left(x+1\right)^4+x^2\cdot\left(x+1\right)^2+2x\left(x+1\right)+1\)
\(=\left(x+1\right)^2\cdot\left[\left(x+1\right)^2+x^2\right]+2x^2+2x+1\)
\(=\left(2x^2+2x+1\right)\left(x^2+2x+1+1\right)\)
\(=\left(2x^2+2x+1\right)\left(x^2+2x+2\right)\)
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)
bạn dặt x^2+3x+5 là y nhé:
phương trình<=> 8y^2+7y-15
đến đó tìm được y tìm tiếp x nhé!
\(x^7+x^5+x^4+x^3+x^2+1\)
\(=x^7+x^6-x^6-x^5+2x^5+2x^4-x^4-x^3+2x^3+2x^2-x^2-x+x+1\)
\(=\left(x^7+x^6\right)-\left(x^6+x^5\right)+\left(2x^5+2x^4\right)-\left(x^4+x^3\right)+\left(2x^3+2x^2\right)-\left(x^2+x\right)+\left(x+1\right)\)
\(=x^6.\left(x+1\right)-x^5.\left(x+1\right)+2x^4\left(x+1\right)-x^3\left(x+1\right)+2x^2\left(x+1\right)-x\left(x+1\right)+\left(x+1\right)\)
\(=\left(x+1\right)\left(x^6-x^5+2x^4-x^3+2x^2-x+1\right)\)