SOLUTION: A rain gutter is formed by bending up the sides by x inches of a 30-inch wide rectangular metal sheet as shown in the figure. (a) Find a function that models the cross-sectional a

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Question 515179: A rain gutter is formed by bending up the sides by x inches of a 30-inch wide rectangular metal sheet as shown in the figure.
(a) Find a function that models the cross-sectional area of the gutter in terms of x.
(b) Find the value of x that maximizes the cross-sectional area of the gutter.
(c) What is the maximum cross-sectional area for the gutter?

Answer by Earlsdon(6294)   (Show Source): You can put this solution on YOUR website!
I don't see the figure to which the problem refers so I'll assume that the sides are bent up at right angles.
a) If the two sides measure x inches each and the sheet metal was 30 inches wide to begin with, then the cross-sectional area can be expressed by the function:


b) If you were to graph this function you would see a parabola that opens downward. The x-value at the maximum point (called the vertex) can be found by:
where a = -2 and b = 30.


c) The maximum cross-sectional area is found by substituting this value of x into the function for the area.
Substitute x = 7.5
Evaluate.

sq.in.

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