# How do you write the formula for the nth term given 1.2, 2.4, 4.8, 9.6,...?

May 7, 2016

$0.6 \times {2}^{n}$
Its 1st term $a = 1.2$
Its common ratio $r = \frac{2.4}{12} = \frac{3.8}{2.4} = \frac{9.6}{4.8} = \ldots = 2$
${t}_{n} = a \cdot {r}^{n - 1} = 1.2 \times {2}^{n - 1} = 0.6 \times {2}^{n}$