How can you tell when a quadratic equation has two identical, rational solutions?

when the radicand is negative

when b in the quadratic formula is greater than the radicand

when the radicand equals zero

when the radicand is not a perfect square

Question

How can you tell when a quadratic equation has two identical, rational solutions?

 when the radicand is negative

 when b in the quadratic formula is greater than the radicand

 when the radicand equals zero

 when the radicand is not a perfect square

anonymous · Answer

You can tell when the part taht you Add or Substract is ZERo

goformit100 · Answer

i think when the radicand is not a perfect square

anonymous · Answer

Since it is zero then the solutions will NOT DIFFER

anonymous · Answer

The question remains - how to ensure they are rational ?

anonymous · Answer

Well - have you you ever used/heard of Vietta Formula ?

anonymous · Answer

Look up Vieta theorem or Vieta Formula - and consider the special case in which $$r_{1} = r_{2}$$

anonymous · Answer

Radicand must be zero

anonymous · Answer

And sum of roots is in this case $$2*r_{1}$$

anonymous · Answer

So if $$r_{1} $$ is rational - then sum of roots is rational