The problem
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i dont understand the step 3,
I understand were we get 3xx = 3squared but what follows +3 it confuses me
Answer provided by our tutors
Clicking on a particular solution step can be the fastest way to review the logic which is employed. It can also avoid confusion by beginning a simplification with 'a few steps' rather than 'a lot of steps' (user the 'Options' tab to modify the number of solution steps).
The '3x' term is multiplied through the parenthetic term (x-y), hence 3x becomes 3xx and 3x(-y).
Notice that the simplification is clearer when using 'a few steps':
