If the n'th term of the A.P, -1,4,9,14...is 129.find thevalue of n.
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-1,4,9,14.......129
first term = a = -1
common difference = d = 4- (-1) = 4+1 = 5
n'th term = Tn = 129
number of terms = n = ?
Tn = a+(n-1)d
129 = -1+(n-1)5
129+1 = 5n -5
130+5 = 5n
135 = 5n
135/5 = n
27 = n
first term = a = -1
common difference = d = 4- (-1) = 4+1 = 5
n'th term = Tn = 129
number of terms = n = ?
Tn = a+(n-1)d
129 = -1+(n-1)5
129+1 = 5n -5
130+5 = 5n
135 = 5n
135/5 = n
27 = n
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