Answer
$d=2.2, a_1=-9$
Work Step by Step
With $a_4=-2.4$, the value of $a_6$ can be found by adding the common difference $d$ twice.
Since $a_4=-2.4$ and $a_6=2$, then:
\begin{align*}
a_4+2d&=a_6\\
-2.4+2d&=2\\
2d&=2+2.4\\
2d&=4.4\\
d&=\frac{4.4}{2}\\
d&=2.2
\end{align*}
To find $a_1$, use the formula $a_n=a_1+d(n-1)$ to obtain:
\begin{align*}
a_6&=a_1+2.2(6-1)\\
2&=a_1+2.2(5)\\
2&=a_1+11\\
2-11&=a_1\\
-9&=a_1
\end{align*}
