the length of a rectangle is 2 more than its width. find the perimeter of this rectangle if its 15ft^2

Question

the length of a rectangle is 2 more than its width , find the perimeter of the rectangle of 15ft^2

Answer 1

Let A be Area, a its length, and b its width. Then

A=15ft^2, a=b+2

p=(a+b)/2

A=a*b=b(b+2)=15ft^2

b^2+2b-15=0.

b=3

a=5

P=16

 

 

Answer 2

Hi Jennifer,

 

I'm assuming the 15 ft² at the end of the problem is the area.

 

(1) L = W + 2

 

(2) L·W = 15

 

solve for W by dividing by L

 

W = 15/L

 

substitute W into the first equation

 

L = 15/l + 2

 

multiply by L

 

L² = 15 + 2L

 

get all terms on one side 

 

L² -2L - 15 = 0

 

factors as: (L - 5)(L + 3) = 0

 

We get L = 5 or L = -3 but a length can't be negative so L = 5

 

If L = 5 , then W = 3

 

Perimeter = 2(L +W) = 2(5 + 3) = 2(8) = 16

 

perimeter = 16 feet