How to see it
You can only combine like terms: the same letter. Four x and two x are six x. Three y take away one y is two y. Think of x and y as different fruits. You cannot add apples to bananas. Brackets: the number outside multiplies everything inside. Three lots of x plus 4 is 3x plus 12.
A worked example
4x plus 2x is 6x. 3y take away y is 2y. So 6x plus 2y. And 2 lots of 3x plus 5: 2 times 3x is 6x, 2 times 5 is 10. 6x plus 10.
The common mistake: multiplying only the first term out of a bracket
The trap is multiplying only the first term: 3(x + 4) becoming 3x plus 4. The 3 belongs to everything in the bracket. And 4x plus 3y does not become 7xy.
Try one
Expand 5 lots of 2x plus 1.
- A10x + 1
- B10x + 5
- C7x + 6
- D10x + 6
Show the answerHide the answer
Right: B, 10x + 5