Answer:
150 bikes, $10,500 minimum manufacturing cost
Explanation:
5x^2 - 1500x + 123000 is represented by a parabolic graph that opens up. You could easily estimate the x value at which C(x) is at a minimum, as well as the smallest C(x) value.
Or you could do this problem algebraically by finding the vertex of the parabola. The results MUST be the same as before.
-b
The equation of the axis of symmetry of this curve is x = ---------
2a
... which here is x = 1500
--------- = 150 units (150 bikes)
2(5)
Evaluating C(x) (see the problem statement) at x = 150 leads to finding the minimum cost. I like to use synthetic division to evaluate polynomials. Here, the divisor would be 150 and the coefficients of the quadratic would be
5 -1500 123000
Setting up synthetic division, we get:
150 / 5 -1500 123000
750 -112500
--------------------------------------
5 -750 10500
The remainder is $10,500. This is the minimum cost of this manufacturing operation.