## Algebra 2 (1st Edition)

$y=0.4 \times 4^x$
Here, we have $6.4 =ab^2; 409.6 =ab^5$ $\dfrac{6.4}{b^{2}}=409.6$ This gives: $b=\sqrt [3] {64} =4$ Then, $a= \dfrac{6.4}{16} =0.4$ Hence, $y=0.4 \times 4^x$