In an AP,the sum of its first n terms is n^2 - 2x. Find its 18th term
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when n = 1
n²-2x
1²-2x
1-2x
a = 1-2x
when n= 2
n²-2x
2²-2x
4-2x
a2 = 4-2x
d= 4-2x-(1-2x)
4-2x-1+2x
3
n=18
an = a +(n-1)d
a18 = 1-2x +(18-1)3
= 1-2x+51
= 52-2x
n²-2x
1²-2x
1-2x
a = 1-2x
when n= 2
n²-2x
2²-2x
4-2x
a2 = 4-2x
d= 4-2x-(1-2x)
4-2x-1+2x
3
n=18
an = a +(n-1)d
a18 = 1-2x +(18-1)3
= 1-2x+51
= 52-2x
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