# The function #y=2x^3-3ax^2 + 6# is decreasing only on the interval (0,3). Find #a#?

##### 1 Answer

The answer is

#### Explanation:

If the function is decreasing on the interval (0, 3), that means its derivative must be negative on this interval. So first let's calculate the derivative, using the power rule:

So we know that the derivative

No matter what

But we also know that when

To double check this, we can plug in

graph{2x^3 - 9x^2 + 6 [-3, 5, -26.6, 13.4]}

And we see that it is decreasing on the interval (0, 3).