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Find 
lim_(x rarr-3)(sqrt(4x+28)-4)/(x+3).
Choose 1 answer:
(A) 
(1)/(2)
(B) 1
(C) 2
(D) The limit doesn't exist

Find limx34x+284x+3 \lim _{x \rightarrow-3} \frac{\sqrt{4 x+28}-4}{x+3} .\newlineChoose 11 answer:\newline(A) 12 \frac{1}{2} \newline(B) 11\newline(C) 22\newline(D) The limit doesn't exist

Full solution

Q. Find limx34x+284x+3 \lim _{x \rightarrow-3} \frac{\sqrt{4 x+28}-4}{x+3} .\newlineChoose 11 answer:\newline(A) 12 \frac{1}{2} \newline(B) 11\newline(C) 22\newline(D) The limit doesn't exist
  1. Identify the form: Identify the form of the limit.\newlineWe need to find the limit of the function (4x+284)/(x+3)(\sqrt{4x+28}-4)/(x+3) as xx approaches 3-3. Let's first substitute x=3x = -3 into the function to see if the limit can be directly calculated.\newlinelimx3(4x+284)/(x+3)=(4(3)+284)/((3)+3)\lim_{x \to -3}(\sqrt{4x+28}-4)/(x+3) = (\sqrt{4(-3)+28}-4)/((-3)+3)\newline=(12+284)/0= (\sqrt{-12+28}-4)/0\newline=(164)/0= (\sqrt{16}-4)/0\newline=(44)/0= (4-4)/0\newline=0/0= 0/0\newlineThis is an indeterminate form, so we cannot directly calculate the limit. We need to use algebraic manipulation to simplify the expression.
  2. Apply algebraic manipulation: Apply algebraic manipulation to simplify the expression.\newlineTo eliminate the indeterminate form, we can multiply the numerator and the denominator by the conjugate of the numerator. The conjugate of 4x+284\sqrt{4x+28}-4 is 4x+28+4\sqrt{4x+28}+4.\newlinelimx34x+284x+34x+28+44x+28+4\lim_{x \to -3}\frac{\sqrt{4x+28}-4}{x+3} \cdot \frac{\sqrt{4x+28}+4}{\sqrt{4x+28}+4}
  3. Perform the multiplication: Perform the multiplication.\newlineNow, we multiply the numerators and the denominators separately.\newlineNumerator: (4x+284)(4x+28+4)=(4x+28)16(\sqrt{4x+28}-4)(\sqrt{4x+28}+4) = (4x+28) - 16\newlineDenominator: (x+3)(4x+28+4)(x+3)(\sqrt{4x+28}+4)
  4. Simplify the expressions: Simplify the resulting expressions.\newlineSimplify the numerator:\newline(4x+28)16=4x+12(4x+28) - 16 = 4x + 12\newlineSimplify the denominator:\newlineWe leave it as is for now: (x+3)(4x+28+4)(x+3)(\sqrt{4x+28}+4)\newlineNow the limit expression looks like this:\newlinelimx34x+12(x+3)(4x+28+4)\lim_{x \to -3}\frac{4x + 12}{(x+3)(\sqrt{4x+28}+4)}
  5. Factor out common terms: Factor out common terms.\newlineWe notice that the numerator has a term 4x+124x + 12 which can be factored as 4(x+3)4(x + 3).\newlinelimx34(x+3)(x+3)(4x+28+4)\lim_{x \to -3}\frac{4(x + 3)}{(x+3)(\sqrt{4x+28}+4)}\newlineNow we can cancel out the (x+3)(x+3) term in the numerator and denominator, as long as x3x \neq -3.\newlinelimx34(4x+28+4)\lim_{x \to -3}\frac{4}{(\sqrt{4x+28}+4)}
  6. Evaluate the limit: Evaluate the limit.\newlineNow that the expression is simplified, we can substitute x=3x = -3 to find the limit.\newlinelimx34(4x+28+4)=4(4(3)+28+4)\lim_{x \to -3}\frac{4}{(\sqrt{4x+28}+4)} = \frac{4}{(\sqrt{4(-3)+28}+4)}\newline=4(12+28+4)= \frac{4}{(\sqrt{-12+28}+4)}\newline=4(16+4)= \frac{4}{(\sqrt{16}+4)}\newline=44+4= \frac{4}{4+4}\newline=48= \frac{4}{8}\newline=12= \frac{1}{2}

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