6. DETAILS Ship A leaves port sailing north at a speed of 20 mph. Four hours later, Ship B leaves the same port sailing east at a speed of 15 mph. (a) What is the distance between the ships 7 hr after Ship A has left port? (Round your answer two decimal places.) mi (b) How fast is the distance between the ships changing at that instant? (Round your answer two decimal places.) mph 7 DETAILS Find an equation of the tangent line to the graph of the function f defined by the equation at the indicated point. Give your answer in the slope-intercept form. 2x2 + 3xy + 2y2 - 16x - 19y + 38 = 0; (3, 4) 8 DETAILS Suppose the distance s (in feet) covered by a particle moving along a straight line after t seconds is given by the function s = f(t) = to + 6t . You must include the units of measurement for each part. (a) Calculate the average velocity of the particle over the time intervals [5, 6]? fu/sec (b) Calculate the (instantaneous) velocity of the particle when t = 5? fu/sec