given sum of first n of the arithmatic sequence= n^2, find T(10).
Difference between two consecutive arithmatic sequence is the last term:T(n)=S(n)-S(n-1)
e.g. T10 =S10-S9 = 10^2 - 9^2 =19
This technicque is quite useful .
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reminder:
T(n)= a + (n-1)d to find T(10).
sum of arithmatic sequence is 頭加尾乘項數除2.
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