Subjects calculus

Limit Growth 3De90D

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Question: top-left: none center: lim x→∞ (4^x + 9^x) ──────────── x )^(1/x) Graph shape: none visible; only a mathematical limit expression with a large parenthesized fraction raised to the power 1/x.
1. **State the problem.** We want to find $$\lim_{x\to\infty}\left(\frac{4^x+9^x}{x}\right)^{1/x}.$$ 2. **Identify the dominant term.** As $x\to\infty$, the term $9^x$ grows faster than $4^x$, so the numerator is dominated by $9^x$. Factor out $9^x$: $$4^x+9^x=9^x\left(\frac{4^x}{9^x}+1\right)=9^x\left(\left(\frac{4}{9}\right)^x+1\right).$$ 3. **Rewrite the expression.** Substitute that into the limit: $$\left(\frac{4^x+9^x}{x}\right)^{1/x}=\left(\frac{9^x\left(\left(\frac{4}{9}\right)^x+1\right)}{x}\right)^{1/x}.$$ Split the $1/x$ power across the factors: $$=\left(9^x\right)^{1/x}\left(\left(\frac{4}{9}\right)^x+1\right)^{1/x}\left(\frac{1}{x}\right)^{1/x}.$$ 4. **Simplify each factor.** The first factor is $$\left(9^x\right)^{1/x}=9.$$ The second factor satisfies $$\left(\frac{4}{9}\right)^x\to 0,$$ so $$\left(\left(\frac{4}{9}\right)^x+1\right)^{1/x}\to 1^{1/x}=1.$$ The third factor is $$\left(\frac{1}{x}\right)^{1/x}.$$ Since $\frac{1}{x}\to 0^+$ and $\lim_{x\to\infty}x^{1/x}=1$, we get $$\left(\frac{1}{x}\right)^{1/x}\to 1.$$ 5. **Combine the limits.** Therefore, $$\lim_{x\to\infty}\left(\frac{4^x+9^x}{x}\right)^{1/x}=9\cdot 1\cdot 1=9.$$ 6. **Final answer.** $$\boxed{9}$$