Question

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

Answer 1

x+x^2=20
x^2+x-20=0
x^2+5x-4x-20=0
x(x+5)-4(x+5)=0
(x+5)(x-4)=0
two solutions: x+5=0 or x-4=0
Since x is positve, consider second solution giving
x=4

Answer 2

what ^^ said! :)