Need help fast please!

how do you factor the following please help, i dont understand:
1) 3x^2+3x-36
2)10x^2+195-15
3)-8x^2+26x-15
4)2x^3-72
5)5x^5-45x

1) 3x^2+3x-36
= 3 (x^2 +x -12)
= 3(x +4)(x -3)

2)10x^2+195-15
= 10x^2 +180
= 10 (x^2 +18)

3)-8x^2+26x-15
= - (8x^2 - 26x +15)
= - ( 4x -3 )(2x -5 )
= ( 3 -4x) (2x-5)

4)2x^3-72
= 2 (x^3 -36)

5)5x^5-45x
= 5x( x^4 -9)
= 5x (x^2 -3)(x^2 +3)

5) 5x (x^5 -9x)