We add and subtract polynomials by grouping like terms.
We therefore first define like terms, how to group them and then how to add and subtract them in order to simplify polynomials. Examples and questions and their solutions are included.
An online calculator to expand ans simpliy polynomials may be used to check answers to the examples and exericses presented.
Like terms in a polynomial are terms with the same variable(s) and the same power.
Add and simplify \( \; 4 x + 6 x \; \)
Solution
Factor \( \; x \; \) out
\( \; 4 x + 6 x = x ( 4 + 6) \; \)
and add \( \; 4 \; \) and \( \; 6 \; \)
\( \; 4 x + 6 x = 10 x \; \)
Add and simplify \( \; - x^3 + 9 x^3 \; \)
Solution
Factor \( \; x ^3 \; \) out and add coefficients
\( \; - x^3 + 9 x^3 = x^3 ( -1 + 9) \; \)
\( \; = 8 x^3 \; \)
Add and simplify \( \; 3 y^2 x^4 - 4 x^4 y^2 \; \)
Solution
Factor \( \; y^2 x^4 \; \) out and add coefficients
\( \; 3 y^2 x^4 - 4 x^4 y^2 = y^2 x^4 ( 3 - 4) \; \)
\( \; = - y^2 x^4 \; \)
You add polynomials by grouping like terms
Add , subtract and simplify:
\( \; ( 5 x^4 + 2 x^3 - 8 x^2 - 10 x + 2) + ( 7 x^3 - 9 x^2 - 5 x + 3 ) - ( - x^3 + 2 x^2 - 3 x + 7 ) \; \)
Solution
Remove parentheses and if a minus sign precedes it multiply all terms inside the parenthesis by \( - 1 \).
\( \; ( 5 x^4 + 2 x^3 - 8 x^2 - 10 x + 2) + ( 7 x^3 - 9 x^2 - 5 x + 3 ) - ( - x^3 + 2 x^2 - 3 x + 7 ) \\
= 5 x^4 + 2 x^3 - 8 x^2 - 10 x + 2 + 7 x^3 - 9 x^2 - 5 x + 3 + x^3 - 2 x^2 + 3 x - 7 \; \)
Group like terms
\( \; (5 x^4) + (2 x^3 + 7 x^3 + x^3 ) + (- 8 x^2 - 9 x^2 - 2 x^2 ) + ( - 10 x - 5 x + 3 x ) + ( 2 + 3 - 7 ) \\
= 5 x^4 + 10 x^3 - 19 x^2 -12 x - 2 \; \)
Expand (if necessary), ddd subtract and simplify the polynomials given below.
a)
\( \; 2x - 3x + 3 y - y + 4 x - 5 y \; \) b)
\( \; - 2(x - 3) - 4 (x + y + 2) - 5y \; \) c)
\( \; 2x^2 - 3 x - 9 y^2 - y + 4 x - 5 y^2 - 5y \; \)
d)
\( \; (-2x+4y-2) - 3(x- 6y-1) + 5 (x - y) \; \) e)
\( \; (5x^2+4y-2) - 5(x - 6y^2 - 1) + 6 (2x - y) \; \)
Expand (if necessary), ddd subtract and simplify the polynomials given below.
a)
\( \; 3 x-3 y \; \) b)
\( \; -6 x -9 y - 2\; \) c)
\( \;2 x^2 -14 y^2 + x - 6 y \; \)
d)
\( \; 17 y + 1 \; \) e)
\( \; 5 x^2+30y^2 + 7 x - 2 y + 3 \; \)