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Maths Exercices
Limits

Evaluating limits

Common techniques in evaluating limits are:

  1. substituting directly
  2. factoring and simplifying
  3. multiplying the numerator and denominator of a rational function by the conjugate of either the numerator or denominator
  4. using a graph or a table of values of the given function.

Find the limit:

Substituting directly:


Find the limit:

Using the product rule,


Find the limit

Factoring and simplifying,

(Note that had you substituted t=2 directly in the original expression, you would have obtained a zero in both the numerator and denominator)


Find the limit

Multiplying both the numerator and the denominator by the conjugate of the numerator,

, yields

(Note that substituting 0 directly into the original expression would have produced a 0 in both numerator and denominator).

Find the limit

You can see that the graph of f(x) approaches 3 as x approaches 0. Thus, the .

(Note that substituting 0 directly into the original expression would have produced a 0 in both numerator and denominator).


Find the limit

You notice that as x approaching 3 from the right, the graph of f(x) goes higher and higher, and that as x approaching 3 from the left, the graph of f(x) goes lower and lower. Therefore,

is undefined.