Answer:y=4 x=3
Step-by-step explanation:9(-9+3y)-4y=11
-81+27y-4y=11 23y=92 y=4 x=3
Answer:
7/16
Step-by-step explanation:
1 3/4 = 7/4
(7/4) / 4 = 7/4 * 1/4
7/16
Answer:
- north and south sides are 38 8/9 ft long
- east and west sides are 17.5 ft long
Step-by-step explanation:
<u>Short answer</u>: area is maximized when half the cost is spent in each of the orthogonal directions. This means the east and west sides will total $350 at $20 per foot, so will be 17.5 feet. The north and south sides will total $350 at $9 per foot, so will be 38 8/9 feet.
The dimensions that maximize the area are 17.5 ft in the north-south direction by 38 8/9 ft in the east-west direction.
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<u>Long answer</u>: If x represents the length of the north and south sides, and y represents the length of the east and west sides, then the total cost is ...
10y +10y +2x +7x = 700
9x +20y = 700
y = (700 -9x)/20
We want to maximize the area:
A = xy = x(700 -9x)/20
We can do this by differentiating and setting the derivative to zero:
dA/dx = 700/20 -9x/10 = 0
350 -9x = 0 . . . . multiply by 10
x = 350/9 = 38 8/9
y = (700 -9(350/9))/20 = 350/20 = 17.5
The north and south sides are 38 8/9 ft long; the east and west sides are 17.5 ft long to maximize the area for the given cost.
