a: \(=\left(x^2+10x\right)\left(x^2+10x+24\right)+128\)
\(=\left(x^2+10x\right)^2+24\left(x^2+10x\right)+128\)
\(=\left(x^2+10x+16\right)\left(x^2+10x+8\right)\)
\(=\left(x+2\right)\left(x+8\right)\left(x^2+10x+8\right)\)
b: \(=\left(x^2+3x-1\right)^2\)