Consider f(x) = v(x). Illustrate that difference quotient of f, ( f(x+h) - f(x) ) / h is equal to 1 / ( v(x+h) + v(x) )
Illustrate that difference quotient of f, quantity f(x+h) minus f(x) divided by h, is equal to 1 divided by quantity square root of (x+h) plus square root of (x).