Question

The area in square feet of a rectangular field is x^2-100x+2400. The width, in feet is x-40. What is the length, in feet?

Answer 1

x-60

Explanation:

You have to factor out the quadratic.

You know that one of the factors is x-40.

To factor:

Find a number that when added to -40, gives you -100, and also when multiplied, gives you 2400.

That such number is -60.

Add an x before it, and you get (x-60)