\(x^4-x^2+10x-25\)
\(=x^4-\left(x^2-10x+25\right)\)
\(=\left(x^2\right)^2-\left(x^2-2\cdot5\cdot x+5^2\right)\)
\(=\left(x^2\right)^2-\left(x-5\right)^2\)
\(=\left[x^2-\left(x-5\right)\right]\left[x^2+\left(x-5\right)\right]\)
\(=\left(x^2-x+5\right)\left(x^2+x-5\right)\)