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### Course: Algebra basics>Unit 7

Lesson 1: Adding & subtracting polynomials

Learn how to simplify polynomials by combining like terms! Discover the power of adding and subtracting terms with the same degree of x. Uncover the magic of removing parentheses and grouping similar terms together to simplify complex expressions. Master the art of polynomial simplification! Created by Sal Khan and Monterey Institute for Technology and Education.

## Want to join the conversation?

• At , Sal says that you can get rid of the parentheses. According to PEMDAS don't you have to complete everything inside of the parentheses before you move on? Why is it okay to ignore the parentheses?
• I'm pretty sure that this only applies if the polynomials inside the parentheses are not in simplest form. If they are in simplest form, then you can remove the parentheses. At least, that's how I do it.
• I don't get why -5t - 3t equals -8t on my textbook, if the subtraction sign also applies to 3t as a negative sign, wouldn't the answer be -2t because you have to change the subtrahend every time, -3t turns into 3t, then you subtract, it becomes -2t. I don't really get it.
• That only applies if you are subtracting a negative number. So if the textbook said -5t - - 3t, you would be absolutely right.

The best way to look at it would be as -5t + -3t = -8t.
• Why do you have to distribute a negative?
• Good question. If you have -4 -3 and you want to factor out a negative one, you would write -1(4+3). Think of the negative sign and the parenthesis as a negative one.
• Is the process the same when you are subtracting?
• Yes. You follow the same process, but flip the sign of each term in the polynomial that you are subtracting. Then you add like normal.
• how would you combine the terms if they had different exponents
• In that case, you wouldn't be able to combine the terms. Could you give me an example so that I could walk you through it? Some scenarios will allow you to add different exponents (after distribution)
• this seems fun
• Isnt that equation 2 trinomials?
(1 vote)
• Yes and no.
Yes, the video is adding 2 trinomials.
No, it is not an equation. It is an algebraic expression. Equations require 2 algebraic expressions connected by an "=" symbol.
• Bro what is this fr I’m so confused
• This may help
The given expression is: (5x² + 8x - 3) + (2x² - 7x + 13x)

First, let's combine the like terms within each set of parentheses:

In the first set of parentheses, we have: 5x² + 8x - 3

In the second set of parentheses, we have: 2x² - 7x + 13x

Now, let's combine the like terms within each set:

For the first set, there are no like terms to combine.

For the second set, the like terms are: -7x and 13x, which combine to give 6x.

Now, we have:

5x² + 8x - 3 + 2x² + 6x

Next, let's combine the like terms across both sets:

5x² + 2x² = 7x²

8x + 6x = 14x

Putting it all together, the simplified form of the expression is:

7x² + 14x - 3
• me looking at these questions that were commented years ago and the nostalgia comes of doing khan academy
• Add the polynomial functions: \large f\left(x\right)=4x^2+3x-5

and \large g\left(x\right)=2x^2-x+1.

Combine the like terms and type in your answer in equation form by clicking on the "Insert Content" with an arrow and select "Equation".
• You should keep it neater, so get rid of the coding type text. just have f(x) = 4x^2 + 3x - 5 and g(x) = 2x^2 - x + 1

Since you are adding the polynomials you have 4x^2 + 3x - 5 + 2x^2 - x + 1.

To add them you do exactly as the instructions say, combine like terms. This just means look for matching variables. For instance 5x^4 - 6x^4 would be like terms since they have x^4. Combining like terms just means to do what the math says to the coefficients. so 5x^4 - 6x^4 means take 5 - 6 since the two are being subtracted. so 5x^4 - 6x^4 = -1x^4 or just -x^4

The three kinds of terms are those that have x^2, x and no variable at all. I will get you started, the non variable terms are -5 and + 1 so combining the gets you -4. can you take it from there?

I will give a different example to further help.

x^4 - 7x^3 + 3 - 5x^4 + 8x^3 + 3
here are the like terms
x^4 - 5x^4 = -4x^4
-7x^3 +8x^3 = x^3
3 + 3 = 6

So now you have -4x^4 + x^3 + 6

Let me know if yous till don't understand