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Adding and Subtracting Polynomials

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In this lesson, we will look at how to add and subtract polynomials.

Adding Polynomials

Adding polynomials involves combining like terms.

Example:

Add the polynomials 5x – 2 + y and –3y + 5x + 2

Solution:

5x – 2 + y + (–3y + 5x + 2)
= 5x + 5x + y – 3y – 2 + 2
= 10x – 2y

Example:

Find the sum of –7x3y + 4x2y2 – 2 and 4x3y + 1 – 8x2y2

Solution:

–7x3y + 4x2y2– 2 + 4x3y + 1 – 8x2y2
= –7x3y + 4x3y + 4x2y2– 8x2y2 – 2 + 1
= –3x3y – 4x2y2– 1

Subtracting Polynomials

To subtract polynomials, remember to distribute the – sign into all the terms in the parenthesis.

Example:

Simplify –4x + 7 – (5x – 3)

Solution:

–4x + 7 – (5x – 3)
= –4x + 7 – 5x + 3
= –4x + 10

Example:

Simplify (5x2 + 2) – (– 4x2 + 7) + (– 3x2– 5)

Solution:

(5x2 + 2) – (– 4x2 + 7) + (– 3x2– 5)
= 5x2 + 2 + 4x2– 7 – 3x2– 5
= 5x2 + 4x2– 3x2 + 2 – 7 – 5
= 6x2– 10



How to add and subtract polynomials?
To add polynomials
1. Combine like terms.
2. Write in descending order.
Example:
1. (4x2 + 8x - 7) + (2x2 - 5x - 12)
2. (5 + 24y3 - 7y2) + (-6y3 + 7y2 + 5)
3. (t2 - t + 5) + (7t2 - 4t - 20)

To subtract polynomials
1. Rewrite the subtraction as addition.
To change subtraction to addition, we must add the opposite, or additive inverse.
2. Combine like terms.
3. Write in descending order.
Example:
1. (4x2 + 8x - 7) - (2x2 - 5x - 12)
2. (6x4 + 3x3 - 1) - (4x3 - 5x + 9)
3. (1.5y3 + 4.8y2 + 12) - (y3 - 1.7y2 + 2y)
Examples of Adding and Subtracting Polynomials
Examples:
1. (2x5 - 6x3 - 12x2 - 4) + (-11x5 + 8x + 2x2 + 6)
2. (-9y3 - 6y2 - 11x + 2) - (-9y4 - 8y3 + 4x2 + 2x)
Adding and Subtracting Polynomials
Adding polynomials and subtracting polynomials is essentially combining like terms of polynomial expressions. When adding and subtracting polynomials, they can either be arranged vertically or grouped according to degree. A knowledge of polynomial vocabulary is important before adding and subtracting polynomials. Multiplying monomials and binomials is another type of operation with polynomials.
Examples:
1. (4x2 - 3x + 2) + (5x2 + 2x - 7)
2. (5x3 + 7x2 - x) + (8x3 + 4x - 5)
3. (8x2 + 2x) - (10x2 + 2x - 9)
4. -(6x3 - 4x) - (2x3 + x2 -2x) Adding and Subtracting Polynomials
Examples:
1. (x2 + 4x + 5) + (6x + 3)
2. 2(x4 + 5x) - 6(x4 + 8x - 3)


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