Year 8 students often make some common mistakes when they are expanding algebraic expressions. Knowing about these mistakes can help them get better at math.

1. Misusing the Distributive Law

• Mistake Rate: About 30% of students don’t use the distributive property correctly. This can lead to wrong answers. For example, if they expand $a(b + c)$ and forget to multiply $a$ with both $b$ and $c$, they might only get $ab$.

2. Forgetting about Negative Signs

• Mistake Rate: Around 25% of students have trouble with negative signs. For instance, when they expand $-2(a + 3)$, they might get $-2a + 3$ instead of the right answer, which is $-2a - 6$.

3. Mixing Up Like Terms

• Mistake Rate: About 20% of students find it tricky to combine like terms after expanding. They might do a good job expanding $2(x + 2) + 3(x + 1)$ into $2x + 4 + 3x + 3$, but then they could mistakenly combine it to $5x + 7$. Actually, this part is correct, but it’s not simplified properly.

4. Ignoring Parentheses

• Mistake Rate: Around 15% of students forget about parentheses altogether, which makes their expansions incomplete.

If Year 8 students know about these common mistakes, it can help them be more ready for harder algebra topics in the future.