How do you factor this?

Question

r(18r^2-39r+20)

Answer 1

r(6r-5)(3r-4)

If this is equal zero then r = 0, r = 5/6, r = 1 1/3

Answer 2

You can look for factors of 18x20 (first and last) that add to 39 (middle). I found 15 and 24. NOW, we break the 39 up with the 15 and 24:

18r^2 - 15r - 24r + 20, and factor by grouping

3r(6r - 5) - 4(6r - 5)

(3r - 4)(6r - 5), and put the r back in front:

r(3r - 4)(6r - 5)

that's it!

Answer 3

r(3r-4)(6r-5)

trial and error