Find the discriminant then state the number of rational, irrational, or imaginary solutions:
11. 9n^2 -3n+2=0
12. y^2 +6y+4=0
13. 9m^2 +6m+1=0
14. -2a^2 -2a+1=0
15. -9b^2 +8b=8
16. -x^2 -9=6x
17. 4r^2 +6=-4r
18. -3b^2 -8b=-1