LT

Test: Quadratic equations

Dynamic incomplete and complete quadratic equations, discriminants, root counts and word modelling.

Question qty: 10
Duration in minutes: 21
Start »

Time left: 00:00:00

Sample questions

  • How many real solutions does x² + (b)x + (c) = 0 have?
  • Solve x² = c.
  • Calculate the discriminant of ax² + (b)x + (c) = 0.
  • Solve ax² + (b)x = 0.
  • Solve x² + (b)x + (c) = 0.
  • Is x a root of x² + (b)x + (c) = 0?
  • A rectangle has area s, and its length is d units greater than its width. Find width and length.
  • Which quadratic equation has roots x1 and x2?

Quadratic equations

A quadratic equation has the form ax² + bx + c = 0, where a ≠ 0. The discriminant D = b² − 4ac determines the number of real roots: two when D > 0, one when D = 0 and none when D < 0.

Methods of solution

Use x = (−b ± √D)/(2a), factorisation or completing the square. Incomplete equations can often be solved more directly. Substitute roots into the original equation and handle brackets carefully, especially when b is negative.