How do you factorise the quadratic equation 2y squared - 2y -24?

2y2 - 2y - 24 has the factors (2y + 6) and (y - 4)

There is a formula, but I always use trial and error.

The factors of the non-x element need to be such that they can be added to give the middle element.

So when you get 24, then you need to be looking at 2,12 - 3,8 - 4,6

When both the second and third element are minus values then there is a plus and a minus in the factors.