When using the distributive property in math, Year 7 students often make some common mistakes. These mistakes can lead to wrong answers when expanding algebraic expressions. Here are some important things to watch out for:

1. Not Distributing to All Terms:

   • A big mistake is only using the distributive property on the first term. For example, in the expression ( a(b + c) ), students need to remember to distribute ( a ) to both ( b ) and ( c ). This means they should get ( ab + ac ). If they don't, their answers may only be partly correct.

2. Using Incorrect Signs:

   • Sometimes, students forget that they need to change signs when dealing with negative numbers. For instance, in ( -a(b - c) ), students must distribute ( -a ) to both ( b ) and ( -c ). This should lead to ( -ab + ac ). Ignoring the negative sign can cause big mistakes.

3. Making Arithmetic Errors:

   • Simple math mistakes can happen while doing the calculations. Research shows that about 30% of mistakes in Year 7 math tests come from wrong calculations, not from misunderstandings of concepts.

4. Forgetting to Combine Like Terms:

   • After distributing, students might forget to combine similar terms. For example, ( 2a + 3a ) should be combined to make ( 5a ). If students don’t realize this, their answers will be incomplete.

5. Missing Variables:

   • In more complex expressions, not recognizing and correctly handling variables can be an issue. It's important to understand each part to avoid mistakes.

By being careful about these common mistakes, Year 7 students can get better at expanding algebraic expressions using the distributive property.