Ta có :
\(x^4-x^2+10x-25\)
\(=\left(x^2\right)^2-\left(x-5\right)^2\)
\(=\left(x^2-x+5\right)\left(x^2+x-5\right)\)
\(x^4-x^2+10x-25=x^4-\left(x^2-10x+25\right)\)
\(=x^4-\left(x-5\right)^2\)
\(=\left(x^2-x+5\right)\left(x^2+x-5\right)\)
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