e.g.
y = x^2 + 6x, find the coordinates of the minimum point
start by differentiating (dy/dx will give you the formula for the gradient)
dy/dx = 2x + 6
minimum point => dy/dx = 0 (remember, at minimum/maximum points the gradient is 0 since at this particular instant the graph isn't increasing or decreasing)
therefore 2x + 6 = 0
2x = 6
x = 3
sub x = 3 into y = x^2 + 6x to get y = 27
the coordinates of your minimum point are therefore (3,27)
(main point: dy/dx will give you the formula for the gradient)