Page 141 - How To Solve Word Problems In Calculus
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F (x) = [A(x)] 2
2
2
= 4x (200 − x )
2
= 800x − 4x 4
F (x) = 1600x − 16x 3
0 = 1600x − 16x 3
2
0 = 16x(100 − x )
x = 0 x = 10
√
Since F (0) = F ( 200) = 0, it follows that the maximum area
√
200 − x 2
occurs when x = 10 and y = = 5. A max = 4xy = 200.
2
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