SOLUTION: Your company has determined that the profit equation (in thousands of dollars) of producing x thousand smartphones is as follows: Profit = –x2 + 110x – 1,000 (If the number

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Question 537590: Your company has determined that the profit equation (in thousands of dollars) of producing x thousand smartphones is as follows:
Profit = –x2 + 110x – 1,000
(If the number of smartphones is 40,000, for example, then x = 40). The break-even point is the number of smartphones sold and produced that would result in a profit of zero.
Use your preferred method for solving the quadratic equation to determine the break-even point. Clearly demonstrate how the answer is determined, and interpret the result in real-life terms.

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
The equation is plotted x-y axes, except
Profit takes the place of y
A profit of zero will occur at the x-intercepts,
or the roots of the equation.
++-x%5E2+%2B+110x+-+1000+=+0+
I can complete the square. first
+-x%5E2+%2B+110x+=+1000+
Multiply both sides by -1
+x%5E2+-+110x+=+-1000+
Take 1/2 of the coefficient of x, square
it, then add it to both sides
+x%5E2+-+110x+%2B+%28110%2F2%29%5E2+=+-1000+%2B+%28110%2F2%29%5E2+
+x%5E2+-+110x+%2B+3025+=+-1000+%2B+3025+
+x%5E2+-+110x+%2B+3025+=+2025+
Both sides are now "perfect squares"
++%28+x+-+55+%29%5E2+=+45%5E2+
Take the square root of both sides
+x+-+55+=+45+
+x+=+100+
And, taking the negative square root of 45,
+x+-+55+=+-45+
+x+=+10+
There are two beak even points. One is at sales of
10,000 smartphones, and the other is at sales
of 100,000 smartphones
check:
(100,0)
P+=+-x%5E2+%2B+110x+-+1000++
+0+=+-%28100%29%5E2+%2B+110%2A100+-+1000+
+0+=+-10000+%2B+11000+-+1000+
+0+=+0+
OK