Hi, I have two questions with derivatives that I'm struggling with:

1) If f(x)= (xlnx)^2, find all points at which the graph of f(x) has a horizontal tangent line.

I really have no idea where to start with this one- how do you find the derivative when the entire ln, not just the function, is squared?

2) Formula for pH is: pH = -ln (H) divided by ln (10).

Ingredients are being added to tomatoes so that the concentration of hydrogen ions in the mixture is given by H(t) = 30-5t-25 (e^(-1/5) - 1) moles per litre. Determine the rate of change of the pH value with respect to time after 10 s.

I'd greatly appreciate any help. Thank you!