Question

The width of a rectangle is the length minus 2 units. The area of the rectangle is 15 units. What is the width, in units, of the rectangle?

Answer 1

Answer:

The answer to your question is width = 3

Step-by-step explanation:

Data

width = w = ?

length = l = ?

Area = 15 units

Process

1.- Write equations to help to solve this problem

   Area of a rectangle = width x length

                                    = w x l                         Equation l

   width = length - 2

         w = l - 2                                                  Equation ll

2.- Substitution

                            A = w x l

                          15 = (l - 2)(l)

3.- Expand

                          15 = l² - 2l

                           l² - 2l - 15 = 0

2.- Solve for l

-Find the prime factors of -15

                          15   3

                            5  5

                             1

     15 = 3 x 5

3.- Factor l² -2l - 15 = 0

                (l - 5)(l + 3) = 0

4.- Find the values of l

                 l₁ - 5 = 0            l₂ + 3 = 0

                 l₁ = 5                 l₂ = -3

The length if the rectangle = 5, it could not be -3, because there are no negative lengths.      

5.- Find w

                   w = l -2

                   w = 5 - 2            

                   w = 3 units