David S. answered • 09/13/16

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CMU Grad Helps You Get the Big Ideas + Little Things in Science/Math

Hi Chantelle,

I'm guessing that you don't have much trouble understanding what is meant by sum: the total resulting from addition. My advice to you is to first look at the terms with the "h" variable and add their coefficients (the numbers that show up in front of them OR 1, if there doesn't seem to be one there). That should help you narrow down your multiple choices to two (big hint).

After you get that down for sure, I'm going to suggest that you add the constants in a certain way that could help you save time and make fewer errors. First add the positive-looking constants together (these look like regular counting numbers and are NOT the coefficients you already added). Did you get 8 for those? Now think about the "minus 2" and the "minus 1" parts of the first two quantities shown as "addition of (-2)" and "addition of (-1)". This is what I mean when I say to add up all the negative constants. You'll get -3 for that, right? Then you will only have to worry about your sign rules for adding the 8 to the -3 rather than trying to do several mixed sign additions.

Let me know if you still need help.