1. **State the problem:** Solve the equation $$\sqrt{3^x \sqrt{9^{x^2-1}}} = 3^{\frac{x+1}{4}}$$.
2. **Rewrite the equation using exponent rules:** Note that $$9 = 3^2$$, so $$9^{x^2-1} = (3^2)^{x^2-1} = 3^{2(x^2-1)}$$.
3. Substitute back:
$$\sqrt{3^x \sqrt{3^{2(x^2-1)}}} = 3^{\frac{x+1}{4}}$$
4. Simplify the inner square root:
$$\sqrt{3^{2(x^2-1)}} = 3^{x^2-1}$$
5. So the left side becomes:
$$\sqrt{3^x \cdot 3^{x^2-1}} = \sqrt{3^{x + x^2 - 1}} = 3^{\frac{x + x^2 - 1}{2}}$$
6. The equation is now:
$$3^{\frac{x + x^2 - 1}{2}} = 3^{\frac{x+1}{4}}$$
7. Since the bases are equal and positive (3), set the exponents equal:
$$\frac{x + x^2 - 1}{2} = \frac{x+1}{4}$$
8. Multiply both sides by 4 to clear denominators:
$$4 \cdot \frac{x + x^2 - 1}{2} = 4 \cdot \frac{x+1}{4}$$
9. Simplify:
$$2(x + x^2 - 1) = x + 1$$
10. Expand left side:
$$2x + 2x^2 - 2 = x + 1$$
11. Rearrange all terms to one side:
$$2x^2 + 2x - 2 - x - 1 = 0$$
12. Simplify:
$$2x^2 + x - 3 = 0$$
13. Use the quadratic formula for $$ax^2 + bx + c = 0$$ where $$a=2$$, $$b=1$$, $$c=-3$$:
$$\Delta = b^2 - 4ac = 1^2 - 4 \cdot 2 \cdot (-3) = 1 + 24 = 25$$
14. Calculate roots:
$$x = \frac{-b \pm \sqrt{\Delta}}{2a} = \frac{-1 \pm 5}{4}$$
15. Find each root:
- $$x_1 = \frac{-1 + 5}{4} = \frac{4}{4} = 1$$
- $$x_2 = \frac{-1 - 5}{4} = \frac{-6}{4} = -\frac{3}{2}$$
16. **Final answer:** $$x = 1$$ or $$x = -\frac{3}{2}$$.
Note: The user’s original solution had a slight error in the quadratic formula denominator; it should be 4, not 10, so the correct roots are as above.
Exponential Equation 57E832
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