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\(x^7+x^2+1\)
\(=\left(x^7+x^6+x^5\right)-\left(x^6+x^5+x^4\right)+\left(x^4+x^3+x^2\right)-\left(x^3+x^2+x\right)+\left(x^2+x+1\right)\)
\(=x^5\left(x^2+x+1\right)-x^4\left(x^2+x+1\right)+x^2\left(x^2+x+1\right)-x\left(x^2+x+1\right)+\left(x^2+x+1\right)\)
\(=\left(x^2+x+1\right)\left(x^5-x^4+x^2-x+1\right)\)

\(x^{16}+x^8+1\)
\(=x^{16}+2x^8+1-x^8\)
\(=\left(x^8+1\right)^2-x^8\)
\(=\left(x^8-x^4+1\right)\left(x^8+x^4+1\right)\)
\(=\left(x^8-x^4+1\right)\left(x^8+2x^4+1-x^4\right)\)
\(=\left(x^8-x^4+1\right)\left[\left(x^4+1\right)^2-x^4\right]\)
\(=\left(x^8-x^4+1\right)\left(x^4-x^2+1\right)\left(x^4+x^2+1\right)\)
\(=\left(x^8-x^4+1\right)\left(x^4-x^2+1\right)\left(x^2-x+1\right)\left(x^2+x+1\right)\)

a)
\(x^7+x^2+1=x^7-x+x^2+x+1\)
\(=x(x^6-1)+x^2+x+1\)
\(=x(x^3-1)(x^3+1)+(x^2+x+1)\)
\(=x(x-1)(x^2+x+1)(x^3+1)+(x^2+x+1)\)
\(=(x^2+x+1)[x(x-1)(x^3+1)+1]\)
\(=(x^2+x+1)(x^5-x^4+x^2-x+1)\)
b)
\(x^8+x+1=x^8-x^2+x^2+x+1\)
\(=x^2(x^6-1)+(x^2+x+1)\)
\(=x^2(x^3-1)(x^3+1)+(x^2+x+1)\)
\(=x^2(x-1)(x^2+x+1)(x^3+1)+(x^2+x+1)\)
\(=(x^2+x+1)[x^2(x-1)(x^3+1)+1]\)
\(=(x^2+x+1)(x^6-x^5+x^3-x^2+1)\)
c)
\(x^8+x^7+1=x^8-x^2+x^7-x+x^2+x+1\)
\(=x^2(x^6-1)+x(x^6-1)+x^2+x+1\)
\(=(x^6-1)(x^2+x)+(x^2+x+1)\)
\(=(x^3-1)(x^3+1)(x^2+x)+(x^2+x+1)\)
\(=(x-1)(x^2+x+1)(x^3+1)(x^2+x)+(x^2+x+1)\)
\(=(x^2+x+1)[(x-1)(x^3+1)(x^2+x)+1]\)
\(=(x^2+x+1)(x^6-x^4+x^3-x+1)\)

một đòn bẫy dài một mét .đặt ở đâu để có thể dùng 3600n có thể nâng tảng đá nặng 120kg?



\(x^8+x+1\)
\(=\left(x^8+x^7+x^6\right)-\left(x^7+x^6+x^5\right)+\left(x^5+x^4+x^3\right)-\left(x^4+x^3+x^2\right)+\left(x^2+x+1\right)\)
\(=x^6\left(x^2+x+1\right)-x^5\left(x^2+x+1\right)+x^3\left(x^2+x+1\right)-x^2\left(x^2+x+1\right)+\left(x^2+x+1\right)\)
\(=\left(x^2+x+1\right)\left(x^6-x^5+x^3-x^2+1\right)\)
\(x^8+x^7+1\)
\(=\left(x^8+x^7+x^6\right)-\left(x^6+x^5+x^4\right)+\left(x^5+x^4+x^3\right)-\left(x^3+x^2+x\right)+\left(x^2+x+1\right)\)
\(=x^6\left(x^2+x+1\right)-x^4\left(x^2+x+1\right)+x^3\left(x^2+x+1\right)-x\left(x^2+x+1\right)+\left(x^2+x+1\right)\)
\(=\left(x^2+x+1\right)\left(x^6-x^4+x^3-x+1\right)\)
\(x^{10}+x^8+1\)
\(=\left(x^2-x+1\right)\left(x^2+x+1\right)\left(x^6-x^2+1\right)\)