Question

what is the difference between a steep and shallow slope

Answer 1

Whether a line is "steep" or "shallow" depends on the slope of the line. In the equation y=mx+b, m is the slope. In your first equation, 1/2x+4, the slope would be 1/2 which means there is 1 increase in the vertical, or y, value for each 2 increases in the horizontal, or x value. This line would be shallow.

Answer 2

If you take one step up or down a steeper slope, your altitude changes more than when you take a step up or down a shallower slope. It's a matter of how much your altitude changes with each step up or down.