Answer:
First tangent line:
Second tangent line:
Notice: slope of -1 means that both 
are equal to -1, so 
So first convert to improper fractions
7 and 7/8=7+7/8=56/8+7/8=63/8
3 and 1/4=3+1/4=12/4+1/4=13/4
so nowe we have
63/8+13/4
convert bottom number to same
which is 8
13/4 times 2/2=26/8
now we have
63/8-26/8=37/8=4 and 5/8
answer is 4 and 5/8
Width=w
length=(40-2w)/2=20-w
A=w(40-w)
A=40w-w²
A'=40-2w=0
2w=40
w=20
20x20 is the size of the pen having the greatest area. this tells us the largest rectangle for a given perimeter is a square
This is false because on 2) x does not equal 3.
