Constants are numbers that stand on their own. They will not have an "x", "y", "z", or any other variable attached to them. They can be small numbers, like "7", or big numbers, like "23,849".

Variables are symbols that stand for numbers that vary. A variable is usually written as a letter, such as "x", "y", or "z".
The difference between constants and variables is that the value of a variable can change, while the value of a constant stays the same.;
, Remember, constants are numbers that stand all alone and never change.



Variables need to be exactly the same for you to add up their coefficients:





"x3 + 3x2" have different exponents, so you cannot add them up.
"x3 + 3x3" both have "x3" as a variable, so you can add them up.


Only add or subtract the value of the coefficient; don't try to add or subtract the variable.





2y2 + 5y2 = 7y2 — not 7y4.
6xy3 - 4 xy3 = 2xy3 — not 2xy.
Define all the constants and the variables.
Add or subtract all constants.
Add or subtract the coefficients of all like variables.
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