Collecting Like Terms #1

“Collecting Like Terms” is a phrase that is used often in mathematics, yet it is a process that can feel a bit arbitrary at first as it relies on several algebraic principles.

The answer shown below is wrong.  Try working your way through the problem backwards, from the answer up. As you find each mistake, try to identify the thinking behind it… what perspective led to the mistake? What should have been done instead?

3x+5-4x+2

=8x-4x+2

=4x-2

.

..

Hint 1: The correct answer to the original problem is: -x+7

Hint 2: What if the problem had been written
3x+4+~^-4x+2
or perhaps
3\cdot x+4+(-4)\cdot x+2

Hint 3: Two mistakes have been made in the work above

Published by

Whit Ford

Math teacher, substitute teacher, and tutor (along with other avocations)

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