How do i prove that this is a right triangle

Which is the graph of f(x) = (4)x? image for option 1 image for option 2 image for option 3 image for option 4

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.

For f(x) = 3x+1 and g(x) = x2 - 6, find (g/f)(x)