Rational Functions Decreasing
1. **Problem:** Determine if the function $$y=\frac{7}{6-x}-9$$ is decreasing over its entire domain.
2. **Step 1:** Find the derivative $$y'$$ to analyze increasing/decreasing behavior.
$$y=7(6-x)^{-1}-9$$
Using the chain rule:
$$y' = 7 \cdot (-1)(6-x)^{-2} \cdot (-1) = \frac{7}{(6-x)^2}$$
3. **Step 2:** Analyze the sign of $$y'$$.
Since $$7 > 0$$ and $$(6-x)^2 > 0$$ for all $$x \neq 6$$, we have $$y' > 0$$ everywhere in the domain.
4. **Step 3:** Conclusion for function 1.
Because $$y' > 0$$, the function is strictly increasing on its entire domain (all real numbers except $$x=6$$).
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5. **Problem:** Determine if the function $$y=-\frac{3}{9-x}+8$$ is decreasing over its entire domain.
6. **Step 1:** Find the derivative.
Rewrite:
$$y = -3(9-x)^{-1} + 8$$
Derivative:
$$y' = -3 \cdot (-1)(9-x)^{-2} \cdot (-1) = -\frac{3}{(9-x)^2}$$
7. **Step 2:** Analyze the sign of $$y'$$.
Since $$3 > 0$$ and $$(9-x)^2 > 0$$ for all $$x \neq 9$$, the derivative is:
$$y' = -\frac{3}{(9-x)^2} < 0$$
8. **Step 3:** Conclusion for function 2.
Because $$y' < 0$$ everywhere in the domain, the function is strictly decreasing on its entire domain (all real numbers except $$x=9$$).
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9. **Problem:** Determine if the function $$y=\frac{1}{2-3x}+4$$ is decreasing over its entire domain.
10. **Step 1:** Find the derivative.
Rewrite:
$$y = (2-3x)^{-1} + 4$$
Derivative:
$$y' = -1 \cdot (2-3x)^{-2} \cdot (-3) = \frac{3}{(2-3x)^2}$$
11. **Step 2:** Analyze the sign of $$y'$$.
Since $$3 > 0$$ and $$(2-3x)^2 > 0$$ for all $$x \neq \frac{2}{3}$$, we have $$y' > 0$$.
12. **Step 3:** Conclusion for function 3.
Because $$y' > 0$$ everywhere in the domain, the function is strictly increasing on its entire domain (all real numbers except $$x=\frac{2}{3}$$).
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**Final answer:**
- Function 1 is increasing.
- Function 2 is decreasing.
- Function 3 is increasing.
Only function 2 is decreasing over its entire domain.