Can you have a rectangle where the Perimeter and Area are both 26?

1 Answer
Feb 25, 2018

We can try to see if there is a rectangle which meets this criteria.

The Area of the Rectangle would be: #l xx w = 26#

The Perimeter of the Rectangle would be: #2l + 2w = 26#

First, we could solve the Perimeter formula for #l#:

#2l + 2w - color(red)(2w) = 26 - color(red)(2w)#

#2l + 0 = 26 - 2w#

#2l = 26 - 2w#

#(2l)color(red)(2) = (26 - 2w)/color(red)(2)#

#l = 13 - w#

Next, we can substitute #(13 -w)# into the formula for Area and solve for #w#

#l xx w = 26# becomes

#(13 - w) xx w = 26#

#13w - w^2 = 26#

#-w^2 + 13w = 26#

#-w^2 + 13w - color(red)(26) = 26 - color(red)(26)#

#-w^2 + 13w - 26 = 0#

#-1(-w^2 + 13w - 26) = -1 xx 0#

#w^2 - 13w + 26 = 0#

We can now use the quadratic equation to solve this problem:

The quadratic formula states:

For #color(red)(a)x^2 + color(blue)(b)x + color(green)(c) = 0#, the values of #x# which are the solutions to the equation are given by:

#x = (-color(blue)(b) +- sqrt(color(blue)(b)^2 - (4color(red)(a)color(green)(c))))/(2 * color(red)(a))#

Substituting:

#color(red)(1)# for #color(red)(a)#

#color(blue)(-13)# for #color(blue)(b)#

#color(green)(26)# for #color(green)(c)# gives:

#w = (-color(blue)(-13) +- sqrt(color(blue)(-13)^2 - (4 * color(red)(1) * color(green)(26))))/(2 * color(red)(1))#

#w = (13 +- sqrt(169 - 104))/2#

#w = (13 +- sqrt(65))/2#

So we can have a rectangle where:

The Length Is: #(13 - sqrt(65))/2#

The Width Is: #(13 + sqrt(65))/2#

Then the Perimeter would be 26 and the Area would be 26