Hello, mt_lapin!
Graph the function: .$\displaystyle y\:=\:20\left(\frac{1}{4}\right)^{x}$
Is this table correct?
. . $\displaystyle \begin{array}{cc}
x & f(x) \\ \hline 3&1280 \\ 2&320 \\ 1&80 \\ 0&20 \\ 1&5 \\ 2&\frac{4}{5} \\3 & \frac{5}{16} \end{array}$ . . . . . Yes!
Also...how could I graph this by hand so that everything fits?
Normally, no one expects a truly accurate graph.
Assuming that we know the shape of: .$\displaystyle [1]\;\;y \:=\:a^x$
. . we can sketch: .$\displaystyle [2]\;\;y \:=\:20\cdot4^{x}$
It is basically a reflection of [1] over the yaxis.
Code:
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