#6
Top 50 Mistake
Errors when expanding negative brackets
"The Negative Neglect"
The Mistake in Action
Expand $-3(2x - 4)$
Wrong: $-6x - 12$
Why It Happens
Students correctly multiply -3 by 2x to get -6x, but then multiply -3 by -4 and keep it negative, forgetting that negative × negative = positive.
The Fix
Remember: When multiplying signs, same signs give positive, different signs give negative.
$$-3 \times 2x = -6x$$ (negative × positive = negative) $$-3 \times (-4) = +12$$ (negative × negative = positive)
Correct answer: $-6x + 12$
Spot the Mistake
Can you identify where this student went wrong?
Expand $-3(2x - 4)$
$-3 \times 2x = -6x$
$-3 \times (-4) = -12$
Click on the line that contains the error.
Related Topics
Learn more about the underlying maths: