Question
Question: If S<sub>n</sub> = n<sup>2</sup> – 2n for an A.P. then T<sub>5</sub> of this A.P. is-...
If Sn = n2 – 2n for an A.P. then T5 of this A.P. is-
A
5
B
7
C
8
D
16
Answer
7
Explanation
Solution
Tn = Sn –Sn–1
Tn = n2 –2n – [(n –1)2 –2 (n –1)]
= n2 –2n – [n2 –2n + 1 –2n + 2]
Tn = 2n –3
T5 = 2 × 5 – 3 = 7