Final answer:
To find the number of computers repaired for the lowest cost using the cost function C = 2.5x^2 - 55x + 425, we apply the vertex formula x = -b/(2a). Jane must repair 11 computers to have the lowest cost.
Step-by-step explanation:
To find out how many computers Jane D. Minted must repair to have the lowest cost, we need to look at the cost function C = 2.5x2 - 55x + 425. This is a quadratic function and its graph is a parabola that opens upwards (since the coefficient of x2 is positive). The lowest point on this parabola, the vertex, will give us the number of computers repaired for the lowest cost. To find the x-coordinate of the vertex, we use the vertex formula x = -b/(2a), where a is the coefficient of x2 and b is the coefficient of x.
Here a is 2.5 and b is -55. Plugging these values into the vertex formula gives us x = -(-55)/(2*2.5) = 55/5 = 11. Therefore, Jane must repair 11 computers to have the lowest cost.