Question

the sum of the first two terms of an arit

Answer 1

SOLUTION:

We are told that;

$\begin{gathered} a+a+d=15 \\ a+2d+a+3d=43 \end{gathered}$

Rewriting, we have;

$\begin{gathered} 2a+d=15 \\ 2a+5d=43 \end{gathered}$

Subtracting the first and second equations, we have;

$\begin{gathered} 4d=28 \\ d=7 \end{gathered}$

and;

$\begin{gathered} 2a+7=15 \\ 2a=8 \\ a=4 \end{gathered}$

Thus, the first four terms of the sequence are;

$4,11,18,25$