Step 1: Use the quadratic formula
For a quadratic equation of the form \( ax^2 + bx + c = 0 \), the roots are given by:
\[
x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}
\]
Step 2: Apply the formula
Here, comparing with \( px^2 - qx + r = 0 \):
- \( a = p \)
- \( b = -q \)
- \( c = r \)
Substituting into the quadratic formula:
\[
x = \frac{-(-q) \pm \sqrt{(-q)^2 - 4(p)(r)}}{2p}
\]
\[
= \frac{q \pm \sqrt{q^2 - 4pr}}{2p}
\]
Thus, the correct answer is:
\[
\frac{q \pm \sqrt{q^2 - 4pr}}{2p}
\]