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Find 
lim_(x rarr-4)(x^(2)-15)/(x^(2)-16).
Choose 1 answer:
(A) 
-(1)/(8)
(B) 
(1)/(8)
(C) 
(19)/(20)
(D) The limit doesn't exist

Find limx4x215x216 \lim _{x \rightarrow-4} \frac{x^{2}-15}{x^{2}-16} .\newlineChoose 11 answer:\newline(A) 18 -\frac{1}{8} \newline(B) 18 \frac{1}{8} \newline(C) 1920 \frac{19}{20} \newline(D) The limit doesn't exist

Full solution

Q. Find limx4x215x216 \lim _{x \rightarrow-4} \frac{x^{2}-15}{x^{2}-16} .\newlineChoose 11 answer:\newline(A) 18 -\frac{1}{8} \newline(B) 18 \frac{1}{8} \newline(C) 1920 \frac{19}{20} \newline(D) The limit doesn't exist
  1. Substitute x=4x = -4: We are asked to find the limit of the function x215x216\frac{x^2 - 15}{x^2 - 16} as xx approaches 4-4. Let's first try to directly substitute x=4x = -4 into the function to see if the limit can be computed this way.
  2. Calculate numerator and denominator: Substitute x=4x = -4 into the function: limx4x215x216=(4)215(4)216\lim_{x \to -4}\frac{x^2 - 15}{x^2 - 16} = \frac{(-4)^2 - 15}{(-4)^2 - 16}
  3. Factor the denominator: Calculate the numerator and the denominator separately:\newlineNumerator: (4)215=1615=1(-4)^2 - 15 = 16 - 15 = 1\newlineDenominator: (4)216=1616=0(-4)^2 - 16 = 16 - 16 = 0
  4. Rewrite the limit expression: We notice that the denominator becomes 00, which means the function is undefined at x=4x = -4. However, this does not necessarily mean that the limit does not exist. We need to factor the denominator to see if there is a common factor that can be canceled out with the numerator.
  5. Conclusion: Factor the denominator: x216x^2 - 16 can be factored as (x4)(x+4)(x - 4)(x + 4).
  6. Conclusion: Factor the denominator:\newlinex216x^2 - 16 can be factored as (x4)(x+4)(x - 4)(x + 4).Now, let's rewrite the limit expression with the factored denominator:\newlinelimx4x215(x4)(x+4)\lim_{x \to -4}\frac{x^2 - 15}{(x - 4)(x + 4)}
  7. Conclusion: Factor the denominator:\newlinex216x^2 - 16 can be factored as (x4)(x+4)(x - 4)(x + 4).Now, let's rewrite the limit expression with the factored denominator:\newlinelimx4x215(x4)(x+4)\lim_{x \to -4}\frac{x^2 - 15}{(x - 4)(x + 4)}We see that there is no common factor between the numerator and the denominator that can be canceled out. Since the denominator is zero and the numerator is non-zero when x=4x = -4, the limit does not exist.

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