Posted by susie on Monday, April 4, 2011 at 7:14pm.
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
(L-4)(L-4) = 0
L = 4
B = 16/L = 4
from the first description
length ---- x
width ---- y
xy = 2x + 2y
xy - 2y = 2x
y(x-2) = 2x
y = 2x/(x-2)
2nd rectangle is 5 by 3, so its perimeter is 30
so now we know 2x+2y = 30
or x+y = 15
y = 15-x
sub that into the other equation, so
2x/(x-2) = 15-x
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 brain-twitch
A 3 by 5 rectangle has a perimeter of 30 ????
Come on Reiny !!!!
i dont get that helppp
i dont get that helppp
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