now, you want a and b such that a*b = -5 and a + 2b = -3
or if trial and error isn't your thing. try the ac method.
multiply the a and c terms, that is the and the , you get
now you want two numbers that when you multiply them you get and when you add them you get the middle term ( ). note that and works.
split the middle term into these two numbers, you get
factor the left side by grouping, you get
now continue using the zero-factor property