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### Course: Algebra (all content)>Unit 10

Lesson 2: Adding & subtracting polynomials

# Adding & subtracting multiple polynomials

Sal simplifies (x³ + 3x - 6) + (-2x² + x - 2) - (3x - 4). Created by Sal Khan and Monterey Institute for Technology and Education.

## Want to join the conversation?

• on khan how can i enter an answer with an exponent? im having trouble entering exponents.
• Usually, a little tab pops up underneath the answer text box with different math operations and symbols such as an exponent.
• At , how can we know if that is a -4 or a minus 4. An how is the product a positive 4? Thanks
• At Sal explains that there is a given number in between the subtraction sign and the parenthesis. In fact at he uses a pink font to draw the 1 into the expression. It is understood that there is an 'invisible' 1 when interpreting negative operations. It is with the use of this understood 1 that we evaluate the expression for simplification. When distributed, -1*-4 equals positive 4.
• G=3t-5t+6
P=-8t^(2)+7t-9
G+P=
Combine like terms.
Hope this helps.
• When do I know when to subtract and add polynomials.
• When do you know how to add & subtract numbers?
The same symbols are used. You add polynomials when there are plus signs. You subtract them when there is a minus sign. Remember to only add/subtract like terms within the polynomials.
• At Sal cancels out the 3x and -3x and leaves it with just x
But doesn't the whole term cancel out so the final answer would be x^3 - 2x^2 - 4?
• There are three terms containing "x"
3x + x - 3x
Yes, 3x and -3x cancel out to 0, but that still leaves the "x" term
Hope this helps.
• What's the difference between adding/subrtracting/multiplying polynomials vertically and horizontally?
• wait so if i have a problem like (2x + 3y - 4) + (x - 3y + 7) and i added all the terms up, which operations do i put into the simplified equation? like for the first term, you add them and it's 3x, but then the two first operations are opposite, for the first one it's + and the second one it's -. so which one do i use in the final answer? please help this assignment is due today.
• Ok, so I know I'm way too late but maybe others have this question too. So when you add the 3y with the -3y they cancel out. Think of it this way: 3 - 3 = 0. So, 3 - 3y = 0. As for adding the -4 and the +7 you do the same thing. Start with the postitive and then subtract the negative. So, 7 - 4 = 3. So... the final answer to this problem is 3x + 3
(1 vote)
• wait correct me if I'm wrong but in equation x to the third cannot be simplified neither can x squared
• x^3 cannot be simplified. Neither can -2x^2. In this equation, there is no x^2.
• simplify -3a (a+b -5) +4 (-2a + 2b) +b (a+ 3b -7)
(1 vote)
• It is just a lot of distributing then combining like terms:
-3a^2 - 3ab + 15a -8a + 8b +ab + 3b^2 - 7b
-3a^2 - 3ab + ab + 3b^2 + 15a - 8a + 8b - 7b
- 3a^2 - 2ab + 3b^2 + 7a + b