Question 844509
{{{f(x)=1/(x+3)}}}
{{{f(x+h)=1/(x+h+3)}}}
{{{f(x+h)-f(x)=1/(x+h+3)-1/(x+3)=(x+3)/((x+3)(x+h+3))-(x+h+3)/((x+3)(x+h+3))}}}
{{{f(x+h)-f(x)=(x+3-x-h-3)/((x+3)(x+h+3))}}}
{{{f(x+h)-f(x)=(-h)/((x+3)(x+h+3))}}}
{{{(f(x+h)-f(x))/h=(-1)/((x+3)(x+h+3))}}}