MCQ
$S_n- S_n- 1 =4$
- A$a_n+1$
- BNone of these
- C$a_n-1$
- ✓$a_n$
✓
Answer
Correct option: D.
$a_n$
formula is $a(n) = S(n) - S(n - 1)$
In general $, S(n) = a(1) + a(2) + ... a(n-1) + a(n)$
In general $S(n-1) = a(1) + a(2) + ... a (n-1)$
If you subtract one from the other, you are left with $a(n)$
because all of the $A's$ from $a(0)$ to $a(n - 1)$ cancel out.
$a(1) - a(1) = 0$
$a(2) - a(2) = 0$
$a(n-1) - a(n-1) = 0$
$S(n) - S(n - 1) = a(n)$
In general $, S(n) = a(1) + a(2) + ... a(n-1) + a(n)$
In general $S(n-1) = a(1) + a(2) + ... a (n-1)$
If you subtract one from the other, you are left with $a(n)$
because all of the $A's$ from $a(0)$ to $a(n - 1)$ cancel out.
$a(1) - a(1) = 0$
$a(2) - a(2) = 0$
$a(n-1) - a(n-1) = 0$
$S(n) - S(n - 1) = a(n)$
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