Question

The sum up to n terms of an AP with first term $a$, last term $l$ and common difference $d$ is

• A. $\frac{n}{2}(2a+(n-1\left)d\right)$
• B. $n(2a+(n-1\left)d\right)$
• C. $\frac{n}{2}(a+l)$
• D. $\frac{n}{2}(a-l)$

Answer 1

Answer: (A), (C)

$\frac{n}{2}(a+l)$

The sum up to $n$ terms of an AP with first term $a$ and common difference $d$ is
$\frac{n}{2}(2a+(n-1\left)d\right)$
And
The sum up to $n$ terms of an AP with first term $a$ and last term $l$ is
$\frac{n}{2}(a+l)$