Question 898780
the steps are shown in the following picture.


steps 1, 2, and 3 are setting up the equations.


step 4 is where the action is.


you need to combine f(a+h) - f(a) in the numerator under a common denominator so you can perform the subtraction.


the common denominator is a*(a+h).


you are multiplying 3*(a+h) by (a/a)


you are multiplying 3/a by (a+h)/(a+h)


this gets the common denominator of a*(a+h) which allows you to combine the numerator under the common denominator.


you then simplify further to get:


(3a-3a-3h)/(a*(a+h)*h) which then simplifies to (-3h)/((a^2+h)*h)


once you've done that, you eliminate the h in the numerator and the denominator because they cancel each other out and you are left with (-3)/(a^2+h)


that's your solution.


you will eventually be taking the limit of that as h approaches 0 which will then get you the derivative of the original expression, but that's in the future.


for now, your solution is:


(-3)/(a^2+h)


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