The product of two consecutive integers is 420. Which quadratic equation can be used to find x, the lesser number?

(x) * (x+1) = 420

x^2 + x = 420

x^2 + x - 420 = 0

a = 1

b=1

c=-420

x = - b + - sq root (b^2 - 4*a*c) / (2*a)

x = - 1 + - sq root (1 - 4*1*-420) / (2*1)

x = [-1 + - sq root (1 + 1680) ] / 2

x = - 1/2 + - 41/2

x1 = 20

x2 = - 21

So, the numbers are 20 and 21

and - 21 and - 20