# 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.

[ Hint : $S 1 = T 1 =a$ $S 2 = T 1 + T 2$ $d= T 2 − T 1]$