Find the slope of a line passing through the points (-7,2) and (6, -11)

If you are just building your payment history, how many points from a perfect score will you possibly miss?

One line passes through (-7,-4) and (5,4) . another line passes through the point (-4,6) and (6,-9)

How do i start to solve? would appreciate a walk-thru! a bird sitting 16ft above the ground in an apple tree dislodges an apple. after how many seconds does the apple land on the ground? (assuming that no branches will interfere with it's fall)