The first three terms of a geometric series are (k+4)(k + 4)(k+4), k k\,k and (2k−15)(2k - 15)(2k−15) respectively, where k k\,k is a positive constant.
Show that k2−7k−60=0k^2 - 7k - 60 = 0k2−7k−60=0.
Hence show that k=12k = 12k=12.
Find the common ratio of this series.
Find the sum to infinity of this series.
Practise Edexcel A Level Old Maths Sequences and Series with exam-style questions for A Level Old Maths. 10 questions, matched to the Edexcel A Level Old Maths (9371) specification and written in Unit exams C1, C2, C3 and C4 plus two applied units (e.g. S1 and M1) style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.