# Year 8

## Number and Algebra

### Indices

Index notation is comparatively modern. The Greek writer Diophantus used the symbol $$\Delta^\text{T}$$ to denote what we would call $$x^2$$ and used K for $$x^3$$. In medieval algebra, Q and C were used instead. Even in the 16th century, people were still writing $$xxx$$ for $$x^3$$. The modern notation didn't appear in texts until late in the 18th century. It is an extremely useful and efficient notation.