Students using the same flawed online solution sheet as the grading TA I am in a small electricity and magnetism class, and I have recently become aware of other students using an online solution sheet (on slader.com).  On the most recent homework, I (who didn't use the online solution sheet) got a significantly worse grade than I expected.  When I read the TAs posted solutions, I realized that he had made all of the same mistakes (the primary one being assuming that the parallel impedance formula is 1/(Z_1)+1/(Z_2) when it is actually 1/(1/(Z_1)+1/(Z_2))) and all of the exact same approximations as the online solution sheet.  It is clear that he basically copied from the online solutions.  What's worse, he marked many of my solutions wrong: both the ones where I had different (more accurate) approximations and the ones that were correct, but different from his incorrect solutions (the professor confirmed that my solutions are correct).

I'm guessing it isn't against the rules for a TA to use an online solution sheet, but the fact that he has been using the same one that many of the students are using means that this entire semester I have been at a significant disadvantage.  I have done well, but the class is curved so there's that also.

What do I do about this?
If the online sheet is incorrect and you suffered because of it, and if you have proof that the TA used that sheet, then you should point out to the professor of the course what has happened. 

But, ask for a a comparison between your answers and those that the TA suggests. This will make it clear. The other students may suffer or not, but that is up to others. You have a right to a correct evaluation of your work and the professor should be made aware of online solutions - especially if they are incorrect and misleading students. 

One set of students getting credit when they've broken rules and other students suffering when they have done the correct thing is the worst outcome possible. 

You don't need to accuse anyone. Point out the online sheet. Point out the (matching) solution rubric. Show your own work and ask for a fair evaluation.