Question

A 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

The error is that the student didn't subtract the r but instead added an r

Explanation:

Step 1: Distribute the negative

6b + 4r - 2b - r

Step 2: Combine like terms

4b + 3r

And we have our final answer!

Answer 2

see below

Explanation:

(6b + 4r) – (2b + r)

Distribute the minus sign to all terms in the last parentheses

6b +4r -2b -r

Combine like terms

4b +3r

They only subtracted the 2b and did not distribute the minus sign to both the 2b and the r

(6b + 4r) – (2b + r) = 6b +4r -2b+r = 4b+5r which is wrong