Lost on setting it up

Question

The perimeter of a rectangle is (4x^2+6x+12) inches and it's length is (x^2+2x+4) inches. Find its width

Answer 1

Hi Heidi,

 

The perimeter of a rectangle is 2(length+width). We are given the length and asked to find the width. Then,

4x^2+6x+12 = 2(length+width)

2x^2 + 3x + 6 = (x^2 + 2x + 4) + width

width = 2x^2 + 3x + 6 - (x^2 + 2x + 4)

= 2x^2 + 3x + 6 - x^2 - 2x - 4

= x^2 + x + 2 inches

Answer 2

P = perimeter = 4x² + 6x + 12

L = length = x²+ 2x + 4

W = width = ?

 

P = 2(L + W) ⇒

 

W = P/2 - L

 

Just plug in the expressions given for P and L into the equation for W, and simplify.  That will be your answer in inches.