Answers

2016-02-06T21:09:22+05:30
A=21
d=21
 a_{n} =420
n=?
 a_{n} =a+(n-1)d
420=21+(n-1)21
(n-1)*21=399
n-1=399/21
n-1=19
n=19+1=20
ans..therefore the 20th term of the AP is 420
0
2016-02-06T21:09:28+05:30
An = 420
a = 21 
d = 21
an = a+(n-1)d
420= 21+(n-1)21
399 = (n-1)21
399/21 = (n-10
19 = n-1
19+1 = n
20 = n
20th term is 420
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