Solve the following word problem by using an equation and factoring. The sum of a positive number and its square is 20. What is the number?

A. 1

B. 2

C. 3

D. 4

E. 5

Number: n

square of number: n^2

sum of n and n^2 is n+n^2=20

Rewriting this equation, we get n^2+n-20=0 = (n+5) (n-4) = 0

Then n+5=0 and n-4=0, so n = - 5 and n = 4.

You must check both results. It could happen that both are correct, or that only one is correct.