If a is uniformly distributed over (-21,25), what is the probability that the roots of the equation x+ax+a+80=0 are both real?

I have no idea what to do with this. For the uniform,
f(y)= 1/(25+21)= 1/46=.02173913. Please help!

Since both roots are real, we need to have a^2 - 4*1*(a+80) > 0, solve for a and go from there. :)