the square of a number is 10 more than 3 times the number

So we have this equation:

n² - 10 = 3n    Rearranging, we have

n² - 3n - 10 = 0   Factoring, we have

(n-5) (n+2) = 0  setting each factor to 0 and solving

n = 5  n= -2

Note that both numbers "work" for the problem.