Question 1143139
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(1) The expression as you show it is<br>
{{{a^2-b^2/2a  -  a - b/6a}}}<br>
Is that right?  If not, you need to use parentheses to make it clear what the expression is.<br>
(2) We don't know how to "do" the problem either, because you haven't said WHAT we are supposed to do.<br>
Be careful when you submit a question to describe it accurately, and to say what it is that is supposed to be done.  Otherwise -- if the only response we can make is to tell you that we don't know what the problem is, so that you have to re-post it -- you are wasting both your time and ours.