Question

If an AP, if common difference $\left(d\right)=-4$, and the seventh term $\left(a_7\right)$ is $4$, find the first term.

Answer 1

$\Rightarrow$$d=-4$

$\Rightarrow$$a_7=4$

$\Rightarrow$Seventh term $=a+6d$

$\therefore$ $a+6d=4$

$\Rightarrow$$a+6(-4)=4$

$\Rightarrow$$a-24=4$

$\Rightarrow$$a=28$