20.3 Rewrite Subtraction as Addition

by Tricia Mintner

| 6 QuestionsNote from the author:

Intro to subtracting polynomials by forcing students to rewrite the problems as addition problems. Multiple formats available for typing in answers. Final question is a student reflection about these problems.

When we subtract polynomials, we have to change the problem into an addition problem by distributing the minus sign to all the terms in the second polynomial. Then we can combine like terms.

1

1

3x + 6y - 2z - 4x + 5y - 4z

3x + 6y - 2z - 4x - 5y + 4z

3x + 6y - 2z - 4x + 5y - 4z

3x + 6y - 2z - 4x + 5y + 4z

2

1

Rewrite as an addition problem:

3

1

Rewrite as an addition problem:

4

1

Rewrite as an addition problem:

5

1

Rewrite as an addition problem:

6

1

How do you feel about rewriting subtraction problems as addition problems?

Strong. I got them all right!

Pretty strong. I had the right answers, but I somehow I type them in wrong.

Okay. I keep forgetting to change ALL the signs in the second polynomial.

Weak. Please show me how to work this out.

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