Additional Mathematics 0606 / Series / 3.453.45: GP fifteenth term and sum near infinity0606/13/O/N/22 — Question 5 · 7 marksMark as done · Save for later · Show all solutions(a)A GP has u15=18u12u_{15}=\tfrac18 u_{12}u15=81u12 and S∞=5S_{\infty}=5S∞=5. Find aaa and rrr.[4]▸ Answer(b)Find the least nnn such that Sn>4.999S_{n}>4.999Sn>4.999.[3]▸ Answer▸ Official mark scheme← 3.82: Descending binomial product: find aaa, bbb, ccc3.47: GP with S3=17.5S_3=17.5S3=17.5 and S∞=20S_\infty=20S∞=20 →
