Find the x-values of all points where the function has any relative extrema. Find the value(s) of any relative extrema. f(x) = x4 - 8x² + 3

Suppose that the price p, in dollars, and the number of sales, x, of a certain item follow the equation 4 p plus 4 x plus 2 pxequals56. suppose also that p and x are both functions of time, measured in days. find the rate at which x is changing when xequals2, pequals6, and startfraction dp over dt endfraction equals1.5.