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Infinite limit and vertical asymptote at x = -5

Consider the function g(x)=3(x+5)2g(x) = \dfrac{3}{(x+5)^2}.

Evaluate lim⁡x→−53(x+5)2\lim_{x \to -5} \frac{3}{(x+5)^2} if it exists as a finite number, or describe the behavior using +∞+\infty or −∞-\infty. Then state whether g(x)g(x) has a vertical asymptote at x=−5x = -5.

Infinite limit and vertical asymptote at x = -5 graph
Hint

Look at what happens to the denominator (x+5)2(x+5)^2 as xx approaches −5-5 from both sides — it's always positive and gets arbitrarily close to 0, so think about what a small positive number in the denominator does to the value of the fraction.

Step-by-step solution

As x→−5x \to -5, the quantity (x+5)2→0+(x+5)^2 \to 0^+, since squaring makes it positive regardless of whether xx approaches from the left or the right. Since the numerator is the constant 3>03 > 0, the fraction 3(x+5)2\frac{3}{(x+5)^2} becomes a positive number divided by a smaller and smaller positive number.

This means the value of g(x)g(x) grows without bound as x→−5x \to -5 from either side, so lim⁡x→−5g(x)=+∞\lim_{x \to -5} g(x) = +\infty. Since both one-sided limits are infinite (and gg is undefined at x=−5x=-5), the function has a vertical asymptote at x=−5x = -5.

Sign of the function near the vertical asymptote

Near x=−5x = -5, is g(x)g(x) positive or negative on both sides?

Hint
Step-by-step solution

The function is positive on both sides near x equals negative five. The numerator is the constant three, which is always positive, and the denominator is a squared quantity, which is always positive regardless of direction of approach. So the fraction stays positive on both the left and right sides, which is why the graph shoots upward toward positive infinity from both directions rather than diverging to different signs.

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