Q2 of 50 Page 21

The terms in two positions of some arithmetic sequences are given below. Write the first five terms of each:

i) 3rd term 34


6th term 67


ii) 3rd term 43


6th term 76


iii) 3rd term 2


5th term 3


iv) 4th term 2


7th term 3


v) 2nd term 5


5th term 2

i) a3 = 34


a6 = 67


a3 = a + 2d and a6 = a + 5d


Solving,a6 = a3 + 3d


d = 11


a2 = 34-11 = 23


a = 23-11 = 12


a4 = 34 + 11 = 45


a5 = 45 + 11 = 56


First 5 terms are 12,23,34,45 and 56


ii) a3 = 43


a6 = 76


a3 = a + 2d and a6 = a + 5d


Solving,a6 = a3 + 3d


d = 11


a2 = 43-11 = 32


a = 32-11 = 21


a4 = 43 + 11 = 54


a5 = 54 + 11 = 65


First 5 terms are 21,32,43,54 and 65


iii) a3 = 2


a5 = 3


a3 = a + 2d and a5 = a + 4d


Solving, a5 = a3 + 2d


d = 0.5


a2 = 2-0.5 = 1.5


a = 1.5-0.5 = 1


a4 = 2 + 0.5 = 2.5


First 5 terms are 1,1.5,2,2.5 and 3


iv) a4 = 2


a7 = 3


a4 = a + 3d


a7 = a + 6d


Solving,a7 = a4 + 3d


d =


a3 = =


a2 = =


a = = 1


a5 = 2 + =


First 5 terms are 1,4/3,5/3,2 and 7/3


v) a2 = 5


a5 = 2


a2 = a + d


a5 = a + 4d


Solving,a5 = a2 + 3d


d = -1


a = 5-(-1) = 6


a3 = 5-1 = 4


a4 = 4-1 = 3


a5 = 3-1 = 2


First 5 terms are 6,5,4,3,2.


Hence solved.


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