Hi...ive been trying to wrap my head around these equations but just can't seem to get it yet.....heres a few examples:

Factorise completely the following expressions:

1) 4t^2 - 9s^2

2) 3s^3 - 15s^2 - 18s

3) 2x^2 - 13x - 24

If any of you guys can work it out clearly for me I would be very greatful!!!

Thanks!!!