Question

The sum of a number and its square is 42. Which equation can be used to find the two numbers for which this is true?

x2 + x = 42
x2 + 2x = 42
x2 + x + 42 = 0
x2 + 2x + 42 = 0

Answer 1

Let x be the number. Then x (the number) plus x^2 (its square) equals 42, so

x^2 + x = 42.

(You can rearrange to x^2 + x - 42 = 0, which factors as (x+7)(x-6)=0 giving x = 6 or x = -7.)