Question

If px² + qx + r = 0 has equal roots , then r = ……………

A) q²/2p

B) q/2p

C) -q²/4p

D) q²/4p

Answer 1

Correct option is (D) q²/4p

Given that quadratic equation \(Px^2+qx+r=0\) has equal roots.

Then its discriminant must be zero.

i.e., D = 0

\(\Rightarrow(-q)^2-4\times p\times r=0\)

\(\Rightarrow q^2-4pr=0\)

\(\Rightarrow4pr=q^2\)

\(\Rightarrow\) \(r=\frac{q^2}{4p}\)

Answer 2

Correct option is D) q²/4p