The second term of an arithmetic sequence is 7. The sum of the first four terms of the arithmetic sequence is 12. Find the first term, a, and the common difference, d, of the sequence.
Let a be the first term
Let d be the common difference
a + d = 7
S4 = 4/2 (2a +3d) = 12
Simultaneous equation:
a+d =7 // x 6
4a +6d = 12
Difference btween these two
6a + 6d = 42
4a +6d = 12
2a = 30
a = 15
d = 7 -a
thus d = -8, a = 15
AT
Related Maths GCSE answers
All answers ▸What are the solutions to x^2+3x+2=0
There are 5 white socks and 3 black socks in a draw. Steven takes out 2 at random. Work out the probability that Steven takes out 2 socks of the same colour.
How do I solve equations with unknowns in the denominators?
A linear sequence starts a + 2b, a + 6b, a + 10b … The 2nd term has value 8 The 5th term has value 44 Work out the values of a and b.