The problem is factoring completely

4xX^2-20x-24
4(X^2-5x-60
4(x-6)(x+1)

12x^2-75
3(X^2-25)=3(X-25)(x+3)

Can someone check these problem for me please.

The first one, second line should read 4(x^2-5x-6). I think that's just a typo. For the 2nd one:

12x^2-75
3(x2-25)
3(x-5)(x+5)