1003107307

We are given a sequence ${\left(a_n\right)}_{n=1}^{\mathrm{\infty }}$ defined recursively by: $a_1=1,a_2=5$ and $a_{n+2}=a_{n+1}-a_n+d$, where $n\in \mathbb{N}$. Find the value of an unknown constant $d\in \mathbb{R}$ and of the term $a_5$ if $a_3=10$.