∑nr=1(∑r−1k=0nCrrCk 2k) is equal to
A stone of mass 2 kg is thrown with a velocity of 20 ms−1 across the frozen surface of a lake and comes to rest after travelling a distance of 100 m. Calculate the frictional force between the stone and the ice.
If 1 is a zero of the polynomial P(a) = x2a2 - 2xa + 3x - 2 . Then x = ___________