\(A=\left(x+1\right)\left(x-2\right)\left(x-3\right)\left(x-5\right)\)
\(A=\left(x+1\right)\left(x-2\right)\left(x^2-3x-5x+15\right)\\ A=\left(x+1\right)\left(x-2\right)\left[x\left(x-3\right)-5\left(x-3\right)\right]\\ A=\left(x+1\right)\left(x-2\right)\left(x-3\right)\left(x-5\right)\)
\(A=\left(x+1\right)\left(x-2\right)\left(x^2-8x+15\right)\)
\(=\left(x+1\right)\left(x-2\right)\left(x-3\right)\left(x-5\right)\)