Moderate -0.3 This is a straightforward geometric sequence question requiring standard formulas. Students need to find the common ratio from two given terms (using ar^4 = -48 and ar = 6 gives r^3 = -8), then apply the nth term formula and sum formula. While it involves multiple steps and algebraic manipulation, it's a routine textbook exercise with no novel problem-solving required, making it slightly easier than average.
The second term of a geometric sequence is 6 and the fifth term is \(-48\).
Find the tenth term of the sequence.
Find also, in simplified form, an expression for the sum of the first \(n\) terms of this sequence. [5]
condone the omission of the brackets round “-2” in the
numerator and / or the denominator
Question 4:
4 | ar = 6 and ar4 = - 48
r = −2
tenth term = 1536
3(1(2)n)
o.e.
1(2)
(2)n 1 | M1
M1
A1
M1
A1 | B2 for r = -2 www
B3 for 1536 www
allow M1 for a = 6÷their r and
substitution in GP formula with their a
and r
c.a.o. | ignore incorrect lettering such as d =-2
condone the omission of the brackets round “-2” in the
numerator and / or the denominator
The second term of a geometric sequence is 6 and the fifth term is $-48$.
Find the tenth term of the sequence.
Find also, in simplified form, an expression for the sum of the first $n$ terms of this sequence. [5]
\hfill \mbox{\textit{OCR MEI C2 Q4 [5]}}