A sequence a1,a2,a3,… a_1, a_2, a_3, \dots\,a1,a2,a3,… is defined by
a1=15an+1=an+d,n≥1 \begin{aligned}a_1 &= 15 \\a_{n+1} &= a_n + d, \quad n \geq 1\end{aligned} a1an+1=15=an+d,n≥1Given a4=6a_4 = 6a4=6
Find the value of ddd.
Find an expression for an a_n\,an in terms of nnn.
231 exam-style questions on WJEC A Level Maths 3.4 Sequences and Series (A-level only), covering 3.4.1 Sequences and Series (A-level only), 3.4.2 Sequences and Series (A-level only), 3.4.3 Sequences and Series (A-level only), 3.4.4 Sequences and Series (A-level only), 3.4.5 Sequences and Series (A-level only), 3.4.6 Sequences and Series (A-level only), and 3.4.7 Sequences and Series (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.