SOLUTION: Bob owns a watch repair shop. he has found that the cost of operating his shop is given by c=3x^2-216x+64, where c is the cost in dollars, and x is the number of watches repaired

Question 611080: Bob owns a watch repair shop. he has found that the cost of operating his shop is given by
c=3x^2-216x+64, where c is the cost in dollars, and x is the number of watches repaired. how many watches must he repair to have the lowest cost?
Answer by nerdybill(7384) (Show Source): You can put this solution on YOUR website!
Bob owns a watch repair shop. he has found that the cost of operating his shop is given by c=3x^2-216x+64, where c is the cost in dollars, and x is the number of watches repaired. how many watches must he repair to have the lowest cost?
.
examining:
c=3x^2-216x+64
we see that it is a parabola that opens upwards (by looking at the coefficient associated with the x^2 term). Therefore, the vertex defines the minimum:
x = -b/(2a)
x = -(-216)/(2(3))
x = 216/6
x = 36 watches

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