Find the common difference and write the next four terms of the following arithmetic progressions:
`-1, (-5)/6, (-2)/3`
Solution
`-1, (-5)/6, (-2)/3`
Here, first term (a1) =−1
Common difference (d) = `a_2 - a_1`
`= -5/6 - (-1)`
`= (-5 + 6)/6`
`= 1/6`
Now, we need to find the next four terms of the given A.P
That is we need to find `a_4, a_5, a_6,a_7`
So using the formula `a_n = a + (n -1)d`
Substituting n = 4, 5, 6, 7 in the above formula
Substituting n = 4, we get
`a_4 = -1 + (4 - 1) (1/6)`
`a_4 = -1 + (1/2)`
`a_4 = (-2 + 1)/2 = (-1)/2`
Substituting n = 5, we get
`a_5 = -1 + (5 -1)(1/6)`
`a_5 = - 1 + 2/3`
`a_5 = (-3 + 2)/3`
`a_5 = - 1/3`
Substituting n = 6, we get
`a_6 = -1 + (6 -1)(1/6)`
`a_6 = -1 + 5/6``
`a_6 = (-6 + 5)/6`
`a_6 = - 1/6`
Substituting n = 7, we get
`a_7 = -1 + (7 -1) (1/6)`
`a_7 = -1 + 1`
`a_7 = 0`
Therefore, the common difference is `d = 1/6` and the next four terms are `-1/2, -1/3, -1/6,0`