1. **State the problem:** Solve the inequality $$2^x + 2 \cdot 2^{-x} - 3 > 0$$.
2. **Rewrite the terms:** Let $$y = 2^x$$. Then $$2^{-x} = \frac{1}{2^x} = \frac{1}{y}$$.
3. **Substitute into the inequality:**
$$y + 2 \cdot \frac{1}{y} - 3 > 0$$
4. **Multiply both sides by $$y$$ (note $$y > 0$$ since $$2^x > 0$$):**
$$y \cdot y + y \cdot 2 \cdot \frac{1}{y} - y \cdot 3 > 0 \implies y^2 + 2 - 3y > 0$$
5. **Rewrite the inequality:**
$$y^2 - 3y + 2 > 0$$
6. **Factor the quadratic:**
$$y^2 - 3y + 2 = (y - 1)(y - 2)$$
7. **Analyze the inequality:**
$$(y - 1)(y - 2) > 0$$ means the product is positive.
This happens when both factors are positive or both are negative.
- Case 1: $$y - 1 > 0$$ and $$y - 2 > 0 \implies y > 2$$
- Case 2: $$y - 1 < 0$$ and $$y - 2 < 0 \implies y < 1$$
8. **Recall $$y = 2^x$$, which is always positive. So the solution in terms of $$x$$ is:**
$$2^x < 1 \quad \text{or} \quad 2^x > 2$$
9. **Solve each inequality:**
- $$2^x < 1 \implies x < 0$$
- $$2^x > 2 \implies x > 1$$
10. **Final solution:**
$$x < 0 \quad \text{or} \quad x > 1$$
This means the inequality holds for all $$x$$ less than 0 or greater than 1.
Exponential Inequality 19403A
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