For example:

I've been doing this by trial and error but it takes too long. I tried googling "factoring quadratics" but when it comes to examples like this, they just use the quadratic equation to find the values of x assuming the whole equation was equal to zero in the first place. Idon't thinkthis helps me.

I need the answer in the form (....)(....) and I don't think the answer on, for example, Solving Quadratic Equations: Examples, does that. What I need is the strategy to find this. I know I'm going to need +7. -5 or -7, +5 at the ends but from there I just have to try so many combinations.