# SPM Practice 1 (Arithmetic Progression) : Question 15

Question 15 (Tricky question! Make sure you try it!)
The sum of n terms of an arithmetic progression is given by the formula ${S}_{n}=\frac{n}{2}\left(5-3n\right)$. Find
(a) the first term,
(b) the common difference,
(c) the tenth term.

Solution: