1. **State the problem:** We are given the function $$y = - (0.8)^x + 5$$ and want to understand its behavior.
2. **Identify the function type:** This is an exponential function of the form $$y = -a^x + c$$ where $$a = 0.8$$ and $$c = 5$$.
3. **Key properties:**
- Since $$0 < a < 1$$, $$a^x$$ is a decreasing exponential function.
- The negative sign in front flips the graph vertically.
- The $$+5$$ shifts the graph upward by 5 units.
4. **Intercepts:**
- To find the y-intercept, set $$x=0$$:
$$y = - (0.8)^0 + 5 = -1 + 5 = 4$$
- To find the x-intercept, set $$y=0$$:
$$0 = - (0.8)^x + 5$$
$$ (0.8)^x = 5$$
Taking natural logarithm on both sides:
$$x \ln(0.8) = \ln(5)$$
$$x = \frac{\ln(5)}{\ln(0.8)}$$
Since $$\ln(0.8) < 0$$, $$x$$ will be negative.
5. **Extrema:**
- Exponential functions of this form have no local maxima or minima except horizontal asymptotes.
6. **Horizontal asymptote:**
- As $$x \to \infty$$, $$ (0.8)^x \to 0$$, so $$y \to 5$$.
- As $$x \to -\infty$$, $$ (0.8)^x \to \infty$$, so $$y \to -\infty$$.
**Final summary:** The graph is a decreasing exponential flipped vertically, shifted up by 5, with y-intercept at 4 and x-intercept at $$x = \frac{\ln(5)}{\ln(0.8)}$$.
Exponential Function B0Ff5D
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