Question

The sum of the first two terms of an arit

Answer 1

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`