Solution
To solve limx→∞(x+3x+2)x, let's proceed step-by-step.
Step 1: Express the function as eln
The limit can be rewritten using the exponential and natural logarithm:
limx→∞(x+3x+2)x=exp(limx→∞xln(x+3x+2)).
Step 2: Simplify the logarithmic term
Let:
y=ln(x+3x+2)=ln(x+2)−ln(x+3).
For large x, approximate each term:
-
ln(x+2)=ln(x(1+x2))=lnx+ln(1+x2).
Using ln(1+u)≈u for small u, ln(1+x2)≈x2.
Thus, ln(x+2)≈21lnx+x2.
-
ln(x+3)=ln(x(1+x3))=lnx+ln(1+x3).
Using ln(1+u)≈u for small u, ln(1+x3)≈x3.
Thus, ln(x+3)≈lnx+x3.
Now, the difference becomes:
ln(x+3x+2)≈(21lnx+x2)−(lnx+x3)=−21lnx+x2−x3.
Step 3: Multiply by x and analyze the dominant term
xln(x+3x+2)≈x(−21lnx+x2−x3).
- The dominant term here is −21xlnx, as it grows faster than the other terms (x2x=2x and −3).
- Thus, xln(x+3x+2)→−∞ as x→∞.
Step 4: Conclude the limit
exp(limx→∞xln(x+3x+2))=exp(−∞)=0.
The limit is:
0.
Would you like further clarifications or a breakdown of specific steps?
Related Questions:
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Tip: When analyzing limits involving exponentials, focus on the dominant terms in logarithmic expansions.