Math Problem Statement

limπ‘₯β†’βˆ’3+π‘₯2+4π‘₯2βˆ’9

Solution

The limit problem you've given is:

lim⁑xβ†’βˆ’3+x2+4x2βˆ’9\lim_{x \to -3^+} \frac{x^2 + 4}{x^2 - 9}

Let's solve this step by step.

Step 1: Factor the denominator

The denominator x2βˆ’9x^2 - 9 can be factored using the difference of squares:

x2βˆ’9=(xβˆ’3)(x+3)x^2 - 9 = (x - 3)(x + 3)

Now the expression becomes:

lim⁑xβ†’βˆ’3+x2+4(xβˆ’3)(x+3)\lim_{x \to -3^+} \frac{x^2 + 4}{(x - 3)(x + 3)}

Step 2: Check the limit as xβ†’βˆ’3+x \to -3^+

When xβ†’βˆ’3+x \to -3^+, the behavior of each part of the fraction must be considered:

  • The numerator x2+4x^2 + 4 approaches 9+4=139 + 4 = 13.
  • The factor xβˆ’3x - 3 approaches βˆ’6-6 because xx is slightly greater than βˆ’3-3 from the right.
  • The factor x+3x + 3 approaches 00, but since xβ†’βˆ’3+x \to -3^+, x+3x + 3 is slightly positive.

Step 3: Analyze the behavior of the limit

Since the numerator approaches 13 (a finite number) and the denominator approaches 0, we analyze the sign of the denominator. The term x+3x + 3 is positive when approaching from the right of βˆ’3-3, and xβˆ’3x - 3 is negative. This means the denominator is approaching 0 from the negative side.

Thus, the limit can be interpreted as:

lim⁑xβ†’βˆ’3+13small negative number=βˆ’βˆž\lim_{x \to -3^+} \frac{13}{\text{small negative number}} = -\infty

Final Answer:

lim⁑xβ†’βˆ’3+x2+4x2βˆ’9=βˆ’βˆž\lim_{x \to -3^+} \frac{x^2 + 4}{x^2 - 9} = -\infty

Would you like more details on any step, or do you have any questions?


Here are 5 related questions for further practice:

  1. lim⁑xβ†’3βˆ’x2+4x2βˆ’9\lim_{x \to 3^-} \frac{x^2 + 4}{x^2 - 9}
  2. lim⁑xβ†’βˆ’3x2βˆ’4x2βˆ’9\lim_{x \to -3} \frac{x^2 - 4}{x^2 - 9}
  3. lim⁑xβ†’0x2+1x2βˆ’1\lim_{x \to 0} \frac{x^2 + 1}{x^2 - 1}
  4. lim⁑xβ†’βˆ’3+x2+9x2βˆ’9\lim_{x \to -3^+} \frac{x^2 + 9}{x^2 - 9}
  5. lim⁑xβ†’2+x2βˆ’4x2βˆ’1\lim_{x \to 2^+} \frac{x^2 - 4}{x^2 - 1}

Tip: Always check the sign of the denominator when it approaches 0 to determine whether the limit tends toward +∞+\infty or βˆ’βˆž-\infty.

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Math Problem Analysis

Mathematical Concepts

Limits
Rational Functions
Difference of Squares

Formulas

(a^2 - b^2) = (a - b)(a + b)

Theorems

Limit Theorem
Difference of Squares Theorem

Suitable Grade Level

Grades 11-12