a,\(x^4+2x^3+10x-25=x^2\left(x^2+5\right)+2x\left(x^2+5\right)-5\left(x^2+5\right)=\left(x^2+5\right)\left(x^2+2x-5\right)\)\(\Rightarrow\left(x^4+2x^3+10x-25\right):\left(x^2+5\right)=x^2+2x-5\)
b,
\(x^3-3x^2+5x-6=x^2\left(x-2\right)-x\left(x-2\right)+3\left(x-2\right)=\left(x-2\right)\left(x^2-x+3\right)\)\(\Rightarrow\left(x^3-3x^2+5x-6\right):\left(x-2\right)=x^2-x+3\)