Spot the equation that does not fit

Exercise and reference answers

Questions

1. Items

   1. x² − 5x + 6 = 0
   2. x³ + x = 0
   3. 2x² + 3 = 0
   4. (x−1)(x+2) = 0

   Reason

   x³ + x = 0 is cubic; the others are quadratic in x.

   Odd item

   x³ + x = 0

Instructions

Four equations are on the board. Tap the one that does not belong with the rest.