Subjects algebra

Exponential System 088289

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Question: User: 9(9^x) = 27^{y+2} and 4^x + 8^y = 1
1. **State the problem:** Solve the system of equations: $$9(9^x) = 27^{y+2}$$ and $$4^x + 8^y = 1$$ 2. **Rewrite the bases as powers of prime numbers:** Note that: $$9 = 3^2, \quad 27 = 3^3, \quad 4 = 2^2, \quad 8 = 2^3$$ 3. **Rewrite each term:** $$9(9^x) = 3^2 \times (3^2)^x = 3^2 \times 3^{2x} = 3^{2 + 2x}$$ $$27^{y+2} = (3^3)^{y+2} = 3^{3(y+2)} = 3^{3y + 6}$$ 4. **Set the exponents equal since bases are the same:** $$2 + 2x = 3y + 6$$ Simplify: $$2x - 3y = 4$$ 5. **Rewrite the second equation:** $$4^x + 8^y = (2^2)^x + (2^3)^y = 2^{2x} + 2^{3y} = 1$$ 6. **Introduce variables:** Let: $$a = 2x, \quad b = 3y$$ Then the system becomes: $$2x - 3y = 4 \implies a - b = 4$$ $$2^a + 2^b = 1$$ 7. **Express $a$ in terms of $b$:** $$a = b + 4$$ 8. **Substitute into the second equation:** $$2^{b+4} + 2^b = 1$$ Rewrite: $$2^b \times 2^4 + 2^b = 1$$ $$2^b (16 + 1) = 1$$ $$17 \times 2^b = 1$$ 9. **Solve for $2^b$:** $$2^b = \frac{1}{17}$$ 10. **Take logarithm base 2:** $$b = \log_2 \left( \frac{1}{17} \right) = -\log_2 17$$ 11. **Find $a$:** $$a = b + 4 = -\log_2 17 + 4$$ 12. **Recall $a = 2x$ and $b = 3y$:** $$2x = 4 - \log_2 17 \implies x = \frac{4 - \log_2 17}{2}$$ $$3y = -\log_2 17 \implies y = -\frac{\log_2 17}{3}$$ **Final answer:** $$x = \frac{4 - \log_2 17}{2}, \quad y = -\frac{\log_2 17}{3}$$