1 Find \(\int 7 x ^ { \frac { 5 } { 2 } } \mathrm {~d} x\).
- Find \(\sum _ { r = 1 } ^ { 5 } \frac { 21 } { r + 2 }\).
- A sequence is defined by
$$\begin{aligned}
u _ { 1 } & = a , \text { where } a \text { is an unknown constant, }
u _ { n + 1 } & = u _ { n } + 5 .
\end{aligned}$$
Find, in terms of \(a\), the tenth term and the sum of the first ten terms of this sequence.