Factor completely
7x^2-31x-20
7x^2-45x-28
5p^2-p-18
7k^2+9k
2b^2+17b+21
28n^4+16n^3-80n^2
3b^3-5b^2+2b
20n^b-97nb+30b
9p^2r+73pr+70r
4x^3+43x^2+3-x
7x^2-32x-60
9r^2-5r-10
9x^2+7x-56
10m^2+89m-9