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Because, that's how math was formed.

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Q: Why can you only add or subtract like terms?
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Related questions

How do you add and subtract like denominator?

You add or subtract only the numerators


How do you know if you will subtract or add in simplifying algebraic expressions?

Only like terms can be subtracted or added in algebraic expressions.


Subtract 9x-9 from 2x plus 3?

You can only add or subtract like terms. So, you subtract 9x from 2x, which gives you -7x. Then subtract -9 from 3 to get -6. And you are left with -7x -6.


How do you simplify by combining like terms?

You add (or subtract) like terms. This will reduce the number of terms in the expression and that is the extent of simplification that you can achieve using this process.


Why do you need to have a common denominator before you subtract or add them?

Because addition and subtraction are defined in terms of like terms.


How is the procedure for adding like terms is similar to the procedure for adding fractions?

Adding like terms can be like adding fractions. You can only add fractions with a common denomonator. You can only combine terms together if they are like. Think of like terms as denomonators. You can only add if they are like.


How do you add and subtract algebraic expressions for example My homework says which expression represents the perimeter in units of this trapezoid?

To add and subtract algebraic expressions the simple rule of like terms applies. In your homework that asks for the expression represents the perimeter in units of this trapezoid you will need to find the like terms and simplify.


To add and subtract fractions less than 1 you add or subtract only the what?

Numerators


Solve the expression by combining any like terms 8w-4w plus 4w equals?

You can add and subtract any like terms. Since 8w, -4w, and 4w are all like terms, since 8, -4, and 4 all tell how many w's you have. This is the essentially same as saying "There are 8 apples, subtract 4 apples, and add 4 apples." (Don't forget that 8w-4w is the same as 8w + -4w). To solve, just add 8, subtract 4, and add 4. Leave w alone. The answer is 4w.


When can you add or subtract coefficients?

You can add and subtract coefficients when they occur in like terms, which means they have the same variable. 2x + 3x = 5x (This addition can take place because all of the variables are x, and are therefore like terms.) and 5y - 2y = 3y (This subtraction can take place because all of the variables are y, and are therefore like terms.) However, if the variables differ, they are unlike terms, and you cannot add or subtract the coefficients. For example: 2a + 3b cannot be added because a and b are different variables, and therefore unlike terms. 3c - 2d cannot occur because c and d are different variables, and therefore unlike terms..


How do you add like terms with squared variables for example 2x plus 4x2?

Terms like 2x and 4x2 are not like terms. In order for terms to be like terms, they must have the exact same variables with the exact same exponents on them. This means that 5x3 and 7x3 are like terms, but 2x and 4x2 are not. To add or subtract like terms, simply add or subtract the coefficients (the numbers in front) and keep the variable part the same. For example, 5x3 + 7x3 = (5 + 7)x3 = 12x3, and 3x2 + 6x2 = (3 + 6)x2 = 9x2. But, since 2x and 4x2 are not like terms, 2x + 4x2 = 2x + 4x2. It just cannot be simplified any more than that.


What are like terms in algebra?

Terms with the same variable(s). In like terms, you may add, subtract, multiply, or divide them. In the equation 3x - 5ax + 9x = 7ax, the 5x and the 10x are like terms because they both contain variables of the same value. Thus, we are allowed to add them up and get 12x. The -5ax and the 7ax are also like terms and if we add 5ax to both sides (after we add 3x to 9x), we'll get the equation 12x = 12ax.