Multiple choice

If the roots of equation $\displaystyle \left( p-q \right) { x }^{ 2 }+\left( q-r \right) x+\left( r-p \right) =0$ are equal, find $\displaystyle (q+r)$

  1. 2r

  2. -2p

  3. 2p

  4. 2q

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

For a quadratic equation Ax^2 + Bx + C = 0 to have equal roots, the discriminant B^2 - 4AC must be 0. Here A = p-q, B = q-r, C = r-p. (q-r)^2 - 4(p-q)(r-p) = 0. Expanding this leads to (q+r-2p)^2 = 0, which implies q+r = 2p.

AI explanation

For the given quadratic equation with equal roots, x = 1 is an obvious root because the sum of the coefficients (p-q) + (q-r) + (r-p) equals zero. Since the roots are equal, both roots must be 1, making the product of the roots 1 * 1 = 1. Using the formula for the product of the roots, which equals the constant term divided by the leading coefficient, we set (r-p)/(p-q) = 1. Solving r - p = p - q yields q + r = 2p.