a: \(4x^4-11x^2-15\)
\(=4x^4-15x^2+4x^2-15\)
\(=x^2\left(4x^2-15\right)+\left(4x^2-15\right)=\left(4x^2-15\right)\left(x^2+1\right)\)
b: \(\left(x^2+x\right)^2-2\left(x^2+x\right)-15\)
\(=\left(x^2+x\right)^2-5\left(x^2+x\right)+3\left(x^2+x\right)-15\)
\(=\left(x^2+x\right)\left(x^2+x-5\right)+3\left(x^2+x-5\right)\)
\(=\left(x^2+x-5\right)\left(x^2+x+3\right)\)
c: \(\left(x^2+x\right)^2+4x^2+4x-12\)
\(=\left(x^2+x\right)^2+4\left(x^2+x\right)-12\)
\(=\left(x^2+x+6\right)\left(x^2+x-2\right)\)
\(=\left(x^2+x+6\right)\left(x+2\right)\left(x-1\right)\)
d: \(x^2+2xy+y^2+2x+2y-15\)
\(=\left(x+y\right)^2+2\left(x+y\right)-15\)
\(=\left(x+y+5\right)\cdot\left(x+y-3\right)\)
