A swimming pool is treated periodically to control harmful bacteria growth. The concentration of bacterial per cm³ after t days is given by
C(t)
in how many days after a treatment will be concentration be minimal ?
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The answer is 4

Step-by-step explanation:

For a quadratic function as given to find the minimum you need to write it in vertex or find the vertex (the vertex in a quadratic function is thr maximum or minimum).

Use the next formula to find the t coordinate of the vertex (the time in the minimum concentration of bateria):

For the given function:

The minimum concentration of bacteria will be after 4 days.