<PRE><B>Question 159731</B>
We know that the perimeter is equal to the length of all the sides
X=width
Y=length

The perimeter of the rectangle=X+X+Y+Y=26

Simplify to 2X+2Y=26

we know that the area is the width multplied by the length
XY=40
We isolate X by dividing Y on both sides X=40/Y

Replace 40/Y for X in the perimeter equation

2(40/Y) +2Y=26

Multiply each term on both sides by Y

80+2Y^2=26Y

subtract 26Y from both sides

80-26Y+2Y^2=0

This is a quadratic equation 
*[invoke solve_quadratic_equation 2, -26, 80]



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