Addition of trinomials — lesson. Mathematics CBSE, Class 7.

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A trinomial algebraic expression is an algebraic expression that has three terms.

The prefix 'tri' in 'trinomial' stands for \(3\) terms.

To add two trinomials, you must:

1) remove the brackets (without changing the signs, because the “\(+\)” sign is in front of the brackets);
2) add the like terms.

Example:

Add trinomials:

(- 5 x^{3} + 3 y - 5 y^{2}) + (8 x^{3} + 5 y^{2} - 2 y)

1) Remove the brackets:

\begin{array}{l} (- 5 x^{3} + 3 y - 5 y^{2}) + (8 x^{3} + 5 y^{2} - 2 y) = \\ = - 5 x^{3} + 3 y - 5 y^{2} + 8 x^{3} + 5 y^{2} - 2 y . \end{array}

2) Find the like terms and add:

\begin{array}{l} \underline{- 5 x^{3}} + 3 y - 5 y^{2} \underline{+ 8 x^{3}} + 5 y^{2} - 2 y = \\ 3 x^{3} \underline{+ 3 y} - 5 y^{2} + 5 y^{2} \underline{- 2 y} = 3 x^{3} + y . \end{array}

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1. Addition of trinomials