Lets remenber the "difference quotient" to a given function f(x):
[tex]\frac{f(x+h)-f(x)}{h}[/tex]Wich give us an aproximation for the slope of a tangent line in a point.
Lets see our expression with the function:
[tex]f(x)=4-5x\text{ , when h=0.1 , h=0.01 and h=0.001}[/tex]We end with the following expressions:
[tex]\frac{(4-5x\text{ + 0.1) - (4-5x)}}{0.1}\text{ , }\frac{(4-5x\text{ + 0.01) - (4-5x)}}{0.01}\text{ , }\frac{(4-5x\text{ + 0.001) - (4-5x)}}{0.001}[/tex]