I don't know how to solve this equation

Question

The height of a door is 2.4 feet longer than the width, and it's front area is 1671.4 square feet. Find the width and height of the door.

Answer 1

w=width

w+2.4=height (or length)

A=l*w

1671.4=w(w+2.4)

w^2+2.4w-1671.4=0

use the quadratic formula with a=1, b=2.4, c=-1671.4

you get...

(-2.4±√(5.76+6685.6))/2

(-2.4±√6691.36)/2

(-2.4±81.8)/2

(-2.4+81.8)/2

79.4/2

w=39.7 feet

h=42.1 feet

check: 39.7*42.1=1671.37≈1671.4