PLS HELP will give brainleist

Suppose that the price p (in dollars) and the weekly sales x (in thousands of units) of a certain commodity satisfy the demand equation 4p cubedplusx squaredequals38 comma 400. determine the rate at which sales are changing at a time when xequals80, pequals20, and the price is falling at the rate of $.20 per week.

Rationalize the denominator- 12x/√x-10

Prove that 16^4-2^13-4^5 is divisible by 11.