When x = 0, the value of f(x) is 2. You can see why below
f(x) = (2^x) + 1
f(0) = (2^0) + 1
f(0) = 1+1
f(0) = 2
So the point (0,2) is on the curve. This is visually shown as the y intercept (the location where the curve crosses the y axis)
When x = 2, the value of f(x) is 5
f(x) = (2^x) + 1
f(2) = (2^2) + 1
f(2) = (4) + 1
f(2) = 5
So (2,5) is another point on this curve
Find the slope of the line through these two points
m = (y2 - y1)/(x2 - x1)
m = (f(2) - f(0))/(2 - 0)
m = (5 - 2)/(2 - 0)
m = 3/2
m = 1.5
The slope as a fraction is 3/2
The slope as a decimal is 1.5
So the rate of change is 1.5