area, perimeter
posted by susie on .
the perimeter of rectangle y is equal to its area. rectangle z has the same perimeter as rectangle y. the length of rectangle z is 5 inches and the width is 3 inches. explain how you can find the length and eidth of rectangle y.

perimeter = 2*5+2*3 = 16
2L + 2 W = 16 so L+W=8
WL = 16 so W = 16/L
L + 16/L = 8
L^2 + 16 = 8L
L^2 8L + 16 = 0
(L4)(L4) = 0
L = 4
B = 16/L = 4 
from the first description
length  x
width  y
xy = 2x + 2y
xy  2y = 2x
y(x2) = 2x
y = 2x/(x2)
2nd rectangle is 5 by 3, so its perimeter is 30
so now we know 2x+2y = 30
or x+y = 15
y = 15x
sub that into the other equation, so
2x/(x2) = 15x
2x = 15x  x^2  30 + 2x
x^2 15x + 30 = 0
by the formula
x = 12.623, and subbing back: y = 2.376
or x = 2.376 and subbing back x = 12.623
(notice 2.376 x 12.623 = 29.992 or 30 as expected 
I must have have a had a braintwitch
A 3 by 5 rectangle has a perimeter of 30 ????
Come on Reiny !!!! 
i don't get that helppp

No help :(

what is the greatest perimeter of a rectangle wiht an area of 39 square feet