Question 517597
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A word about function notation.  P is your profit function.  P(x) is the <i>value of the function P at x</i>.  So, P(5) is the value at 5.  Replace every instance of the variable x with 5 and do the arithmetic.


I'll let you do your own graph.  Your function has a negative lead coefficient, so you will get a parabola that is concave down.


The value of the function, that is the height of the graph at a given point is the amount of profit made for selling the number of phones represented by the x value of that point.  The x-intercepts are the break-even points, i.e. where you neither make money nor lose money.  Function values below the x-axis are negative -- you are losing money.  The vertex of the parabola is the point where you make the maximum possible.  Take the negative of the 1st degree term coefficient and divide it by 2 times the lead coefficient to get the x value that gives you the maximum profit.  


John
*[tex \LARGE e^{i\pi} + 1 = 0]
My calculator said it, I believe it, that settles it
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