5a)
let x represent the length of the pen:
let w represent the width of the pen:
remember: perimeter of a rectangle formula is P = 2x + 2w
so...
260 = 2x + 2w
260 - 2x = 2w
130 - x = w
b) A = 4000
sub in equation from a) for “w”, solve for X
A = X x w
4000 = X x (130 - X)
4000 = 130x - x^2
x^2 -130x -4000 = 0
*use quadratic formula
roots: x = 155.69178573609
x = -25.691785736085
the second root is inadmissible because a length cannot be a negative number, so the first root of 155m approx is the length of the pen if the area is 4000 sq m.
