"Consider the regression line y = x + b where σ 2 ( X ) = 9 and σ 2 ( Y ) = 16 . What is the correlation between x and y ?"

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.