The terms, unu_nun, of a periodic sequence are defined by
u1=5andun+1=10un u_1 = 5 \quad \text{and} \quad u_{n+1} = \frac{10}{u_n} u1=5andun+1=un10Find u2u_2u2, u3u_3u3 and u4u_4u4.
State the period of the sequence.
Find the value of ∑n=151un\sum_{n=1}^{51} u_n∑n=151un.
308 exam-style questions on AQA A Level Maths 1.7 D: Sequences and series, covering 1.7.1 Binomial expansion, 1.7.2 Types of sequence (A-level only), 1.7.3 Sigma notation (A-level only), 1.7.4 Arithmetic sequences and series (A-level only), 1.7.5 Geometric sequences and series (A-level only), and 1.7.6 Sequences and series in modelling (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.