All yvalues are multiplied by c, and the vertical distances are scaled by c. 
All yvalues have a added to them, meaning you shift the graph vertically by a. 

The value of y at x on the new graph is equal to cx on the old graph. The graph is scaled horizontally by 1/c. 
The value of y at x on the new graph is equal to x + a on the old graph. The graph is shifted left by a. 