use discriminant
for
ax²+bx+c=0
the discriminant is b²-4ac
if the discriminant is
1. less than 0, then no real number solutions
2. equal to 0, then there is 1 real number solution
3. greater than 0, then there are 2 real number solutions
-2x²+8x-5=0
a=-2
b=8
c=-5
b²-4ac=8²-4(-2)(-5)=64-40=24>0
2 real number solutions
