01 76 38 08 47
Kartable logo
HomeBrowseSearchLog in

To enjoy 10 free documents.

Kartable logo
HomeBrowseSearchLog in

To enjoy 10 free documents.

  1. Home
  2. 12th grade
  3. Calculus
  4. Exercise : Find the limit of a function of the form f/g

Find the limit of a function of the form f/g Calculus

Find the following limit if it exists.

\lim\limits_{x \to -2}\dfrac{3+2x}{4^x}

We have:

\lim\limits_{x \rightarrow -2} \left(3 + 2x\right) = 3 + 2\left(-2\right) = -1

And:

\lim\limits_{x \rightarrow -2} 4^x = 4^{\left(-2\right)} = \dfrac{1}{16}

Therefore:

\lim\limits_{x \rightarrow -2} \dfrac{3 + 2x}{4^x} = \dfrac{-1}{\dfrac{1}{16}} = -16

\lim\limits_{x \to -2}\dfrac{3+2x}{4^x}=-16

\lim\limits_{x \rightarrow 1} \dfrac{6x - 1}{x^3 - 1}

We have:

\lim\limits_{x \rightarrow 1} \left(6x - 1\right) = 6\left(1\right) - 1 = 5

And:

\lim\limits_{x \rightarrow 1} \left(x^3 - 1\right) = \left(1\right)^3 - 1 = 0

Therefore:

\lim\limits_{x \rightarrow 1} \dfrac{6x - 1}{x^3 - 1} = \dfrac{5}{0} \rightarrow undefined.

The limit does not exist.

\lim\limits_{x \rightarrow -1} \dfrac{x^2 + 2x}{x^5 - 1}

We have:

\lim\limits_{x \rightarrow -1} \left(x^2 + 2x\right) = \left(-1\right)^2 + 2\left(-1\right) = 1 - 2 = -1

And:

\lim\limits_{x \rightarrow -1} \left(x^5 - 1\right) = \left(-1\right)^5 - 1 = -1 - 1 = -2

Therefore:

\lim\limits_{x \rightarrow -1} \dfrac{x^2 + 2x}{x^5 - 1} = \dfrac{-1}{-2} = \dfrac{1}{2}

\lim\limits_{x \rightarrow -1} \dfrac{x^2 + 2x}{x^5 - 1} = \dfrac{1}{2}

\lim\limits_{x \rightarrow 3} \dfrac{3x^2 + x + 1}{6x^2 + 2x}

We have:

\lim\limits_{x \rightarrow 3} \left(3x^2 + x + 1\right) = 3\left(3\right)^2 + \left(3\right) + 1 = 27 + 3 + 1 = 31

And:

\lim\limits_{x \rightarrow 3} \left(6x^2 + 2x\right) = 6\left(3\right)^2 + 2\left(3\right) = 54 + 6 = 60

Therefore:

\lim\limits_{x \rightarrow 3} \dfrac{3x^2 + x + 1}{6x^2 + 2x} = \dfrac{31}{60}

\lim\limits_{x \rightarrow 3} \dfrac{3x^2 + x + 1}{6x^2 + 2x} = \dfrac{31}{60}

\lim\limits_{x \rightarrow -2} \dfrac{3^x}{x^3}

We have:

\lim\limits_{x \rightarrow -2} 3^x = 3^{-2} = \dfrac{1}{3^2} = \dfrac{1}{9}

And:

\lim\limits_{x \rightarrow -2} x^3 = \left(-2\right)^3 = -8

Therefore:

\lim\limits_{x \rightarrow -2} \dfrac{3^x}{x^3} = \dfrac{\dfrac{1}{9}}{-8} = \dfrac{-1}{72}

\lim\limits_{x \rightarrow -2} \dfrac{3^x}{x^3} = \dfrac{-1}{72}

\lim\limits_{x \rightarrow 4} \dfrac{2x - 1}{x^2 - 3^{x-2}}

We have:

\lim\limits_{x \rightarrow 4} \left(2x - 1\right) = 2\left(4\right) - 1 = 7

And:

\lim\limits_{x \rightarrow 4} \left(x^2 - 3^{x-2}\right) = 4^2 - 3^{4-2} = 16 - 3^2 = 16 - 9 = 7

Therefore:

\lim\limits_{x \rightarrow 4} \dfrac{2x - 1}{x^2 - 3^{x-2}} = \dfrac{7}{7} = 1

\lim\limits_{x \rightarrow 4} \dfrac{2x - 1}{x^2 - 3^{x-2}} = 1

\lim\limits_{x \rightarrow 3} \dfrac{5^x}{-2x^2 + 4x + 1}

We have:

\lim\limits_{x \rightarrow 3} 5^x = 5^3 = 125

And:

\lim\limits_{x \rightarrow 3} \left( -2x^2 + 4x + 1\right) = -2\left(3\right)^2 + 4\left(3\right) + 1 = -18 + 12 + 1 = -5

Therefore:

\lim\limits_{x \rightarrow 3} \dfrac{5^x}{-2x^2 + 4x + 1} = \dfrac{125}{-5} = -25

\lim\limits_{x \rightarrow 3} \dfrac{5^x}{-2x^2 + 4x + 1} = -25

The editorial charter guarantees the compliance of the content with the official National Education curricula. Learn more

The courses and exercises are written by the Kartable editorial team, made up of teachers certified and accredited. Learn more

See also
  • Course : Limits of functions
  • Exercise : Make conjecture about limits from graphs
  • Exercise : Identify vertifcal and horizontal asymptotes from graphs
  • Exercise : Find the limit of a polynomial
  • Exercise : Find the limit of an exponential function
  • Exercise : Find the limit of a function of the form f+g
  • Exercise : Find the limit of a function of the form f.g
  • Exercise : Find a zero-denominator limit using factorization
  • support@kartable.com
  • Legal notice

© Kartable 2026