Use the discriminant to determine the number of real solutions of the quadratic equations.

60. (-5xsquared - 4x + 4)= 0

62. (xsquared - 4x + 4) = 0

64. (4/7xsquared -8x + 28) =0

66. (9 + 2.4x - 8.3xsquared)=0

i don't know what it means by discriminant?