Question 942945
Critical values are the roots.


roots:
{{{t=(-5+- sqrt(25-4a*4))/(2a)}}}  and you want the discriminant to be real, not complex with any imaginaries.


{{{25-16a>=0}}}, the requirement for the discriminant.

{{{25>=16a}}};
  Your really want {{{25>16a}}}
{{{25/16>a}}}
different from what you expected.