# 12.2 Finding limits: properties of limits  (Page 2/5)

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## Evaluating the limit of a function algebraically

Evaluate $\text{\hspace{0.17em}}\underset{x\to 3}{\mathrm{lim}}\left(2x+5\right).$

Evaluate the following limit: $\text{\hspace{0.17em}}\underset{x\to -12}{\mathrm{lim}}\left(-2x+2\right).$

26

## Finding the limit of a polynomial

Not all functions or their limits involve simple addition, subtraction, or multiplication. Some may include polynomials. Recall that a polynomial is an expression consisting of the sum of two or more terms, each of which consists of a constant and a variable raised to a nonnegative integral power. To find the limit of a polynomial function, we can find the limits of the individual terms of the function, and then add them together. Also, the limit    of a polynomial function as $\text{\hspace{0.17em}}x\text{\hspace{0.17em}}$ approaches $\text{\hspace{0.17em}}a\text{\hspace{0.17em}}$ is equivalent to simply evaluating the function for $\text{\hspace{0.17em}}a$ .

Given a function containing a polynomial, find its limit.

1. Use the properties of limits to break up the polynomial into individual terms.
2. Find the limits of the individual terms.
4. Alternatively, evaluate the function for $\text{\hspace{0.17em}}a$ .

## Evaluating the limit of a function algebraically

Evaluate $\text{\hspace{0.17em}}\underset{x\to 3}{\mathrm{lim}}\left(5{x}^{2}\right).$

Evaluate $\text{\hspace{0.17em}}\underset{x\to 4}{\mathrm{lim}}\left({x}^{3}-5\right).$

59

## Evaluating the limit of a polynomial algebraically

Evaluate $\text{\hspace{0.17em}}\underset{x\to 5}{\mathrm{lim}}\left(2{x}^{3}-3x+1\right).$

Evaluate the following limit: $\text{\hspace{0.17em}}\underset{x\to -1}{\mathrm{lim}}\left({x}^{4}-4{x}^{3}+5\right).$

10

## Finding the limit of a power or a root

When a limit includes a power or a root, we need another property to help us evaluate it. The square of the limit    of a function equals the limit of the square of the function; the same goes for higher powers. Likewise, the square root of the limit of a function equals the limit of the square root of the function; the same holds true for higher roots.

## Evaluating a limit of a power

Evaluate $\text{\hspace{0.17em}}\underset{x\to 2}{\mathrm{lim}}{\left(3x+1\right)}^{5}.$

We will take the limit of the function as $\text{\hspace{0.17em}}x\text{\hspace{0.17em}}$ approaches 2 and raise the result to the 5 th power.

Evaluate the following limit: $\underset{x\to -4}{\mathrm{lim}}{\left(10x+36\right)}^{3}.$

$-64$

If we can’t directly apply the properties of a limit, for example in $\underset{x\to 2}{\mathrm{lim}}\left(\frac{{x}^{2}+6x+8}{x-2}\right)$ , can we still determine the limit of the function as $x$ approaches $a$ ?

Yes. Some functions may be algebraically rearranged so that one can evaluate the limit of a simplified equivalent form of the function.

## Finding the limit of a quotient

Finding the limit of a function expressed as a quotient can be more complicated. We often need to rewrite the function algebraically before applying the properties of a limit. If the denominator evaluates to 0 when we apply the properties of a limit directly, we must rewrite the quotient in a different form. One approach is to write the quotient in factored form and simplify.

Case of Equilateral Hyperbola
ok
Zander
ok
Shella
Explain why log a x is not defined for a < 0
the sum of any two linear polynomial is what
Momo
how can are find the domain and range of a relations
A cell phone company offers two plans for minutes. Plan A: $15 per month and$2 for every 300 texts. Plan B: $25 per month and$0.50 for every 100 texts. How many texts would you need to send per month for plan B to save you money?
6000
Robert
more than 6000
Robert
can I see the picture
How would you find if a radical function is one to one?
how to understand calculus?
with doing calculus
SLIMANE
Thanks po.
Jenica
Hey I am new to precalculus, and wanted clarification please on what sine is as I am floored by the terms in this app? I don't mean to sound stupid but I have only completed up to college algebra.
I don't know if you are looking for a deeper answer or not, but the sine of an angle in a right triangle is the length of the opposite side to the angle in question divided by the length of the hypotenuse of said triangle.
Marco
can you give me sir tips to quickly understand precalculus. Im new too in that topic. Thanks
Jenica
if you remember sine, cosine, and tangent from geometry, all the relationships are the same but they use x y and r instead (x is adjacent, y is opposite, and r is hypotenuse).
Natalie
it is better to use unit circle than triangle .triangle is only used for acute angles but you can begin with. Download any application named"unit circle" you find in it all you need. unit circle is a circle centred at origine (0;0) with radius r= 1.
SLIMANE
What is domain
johnphilip
the standard equation of the ellipse that has vertices (0,-4)&(0,4) and foci (0, -15)&(0,15) it's standard equation is x^2 + y^2/16 =1 tell my why is it only x^2? why is there no a^2?
what is foci?
This term is plural for a focus, it is used for conic sections. For more detail or other math questions. I recommend researching on "Khan academy" or watching "The Organic Chemistry Tutor" YouTube channel.
Chris
how to determine the vertex,focus,directrix and axis of symmetry of the parabola by equations
i want to sure my answer of the exercise
what is the diameter of(x-2)²+(y-3)²=25