11: =(x+4)(x+5)
12: =(x-5)(x+4)
13: \(=3x^2+3x-2x-2=\left(x+1\right)\left(3x-2\right)\)
14: \(=4x^2+8x-3x-6=\left(x+2\right)\left(4x-3\right)\)
15: \(=4x^2+12x+3x+9=\left(x+3\right)\left(4x+3\right)\)
16: \(=3x^2+9x+x+3=\left(x+3\right)\left(3x+1\right)\)