2a²b²-7ab-15
=（2ab+3)(ab-5)
8x³+4x²-2x-1
=4x²(2x+1)-(2x+1)
=(2x+1)(4x²-1)
=(2x+1)(2x+1)(2x-1)
=(2x+1)²(2x-1）
5x²-15x+2xy-6y
=5x(x-3)+2y(x-3)
=(x-3)(5x+2y)