Question

student simplifies (6b + 4r) – (2b + r) and says that the result is 4b + 5r. Explain the error and describe the correct steps to simplify the expression.

Answer 1

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Explanation:

this was the sample response on edge

The student did not distribute the negative when subtracting. Distributing the negative, the expression is equal to 6b + 4r – 2b – r. Then use the commutative property to rewrite it as 6b – 2b + 4r – r. Then you can use the distributive property to write as (6 – 2)b + (4 – 1)r, which simplifies to 4b + 3r.

Answer 2

Answer & explanation:

The student made an error by adding an r after removing the parentheses instead of subtracting an r.

Correct Steps:

(6b + 4r) – (2b + r)

6b + 4r - 2b - r

4b + 3r