PreCalc
posted by Amy .
Can anyone help with the following problem please...Thank u so much
Let f(x) =9x. For the area above the xaxis and between the lines x= 9 and x=18
a. draw and label a sketch with
the area shaded
b. find the area of the region in
the xyplane under the graph
of f(x)

For this kind of problem, it is always desirable to make a sketch within the limits of the domain, from x=9 to 18.
See:
http://img510.imageshack.us/img510/2928/1291868155.png
Using the formula for the area of a triangle as:
Area = (1/2)base*height
You can find the areas of the two triangles between the function and the xaxis.
If you need further help, don't hesitate to post. 
Amy, please check to see if your question has been answered before posting the same question again.
you asked the same question with only a small change yesterday,
http://www.jiskha.com/display.cgi?id=1291781963
MathMate has gone to some length to answer it again, even creating a picture for you.
make a note of your post by jotting down the time of the first posting, even though it moves off the page, it is then rather easy to find 
Thank you for your help