Quadratic functions: related to parabolas

1) Given a quadratic function y = 2x^2 - 6x + 7, find the coordinates of the vertex by using the method of completing the square.

2) A stone was thrown vertically upwards from the ground. Its height above the ground, s meters, reached in t seconds was given by

s = -5t^2 + 40t

a) Express s in the form a(t - b)^2 + c, where a, b and c are constants.

b) What is the greatest height reached and the time to obtain this height?

Please help and explain concepts. Thanks.