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Limits at Infinity, Part 1

Jun 09, 2015

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Education

Pablo Antuna

In this presentation I present the concept of limits at infinity and the basic technique for solving them. We solve an example step by step.
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Page 1: Limits at Infinity, Part 1
Page 2: Limits at Infinity, Part 1
Page 3: Limits at Infinity, Part 1

What are Limits at Infinity?

Limits at infinity are just like normal limits.

The difference is that x is approaching infinity instead of a number.

limx→∞

f (x)

This means that x is growing without bounds.

Or that it takes values greater than any number you can come upwith.

Page 4: Limits at Infinity, Part 1

What are Limits at Infinity?

Limits at infinity are just like normal limits.

The difference is that x is approaching infinity instead of a number.

limx→∞

f (x)

This means that x is growing without bounds.

Or that it takes values greater than any number you can come upwith.

Page 5: Limits at Infinity, Part 1

What are Limits at Infinity?

Limits at infinity are just like normal limits.

The difference is that x is approaching infinity instead of a number.

limx→∞

f (x)

This means that x is growing without bounds.

Or that it takes values greater than any number you can come upwith.

Page 6: Limits at Infinity, Part 1

What are Limits at Infinity?

Limits at infinity are just like normal limits.

The difference is that x is approaching infinity instead of a number.

limx→∞

f (x)

This means that x is growing without bounds.

Or that it takes values greater than any number you can come upwith.

Page 7: Limits at Infinity, Part 1

What are Limits at Infinity?

Limits at infinity are just like normal limits.

The difference is that x is approaching infinity instead of a number.

limx→∞

f (x)

This means that x is growing without bounds.

Or that it takes values greater than any number you can come upwith.

Page 8: Limits at Infinity, Part 1

What are Limits at Infinity?

Limits at infinity are just like normal limits.

The difference is that x is approaching infinity instead of a number.

limx→∞

f (x)

This means that x is growing without bounds.

Or that it takes values greater than any number you can come upwith.

Page 9: Limits at Infinity, Part 1

The Basic Technique For Solving Limits at Infinity

1. First of all, we find the greatest exponent in our function.

I For example:

2. Then we divide both the numerator and denominator by xn.

I In our example:

Page 10: Limits at Infinity, Part 1

The Basic Technique For Solving Limits at Infinity

To solve these limits we use a basic technique:

1. First of all, we find the greatest exponent in our function.

I For example:

2. Then we divide both the numerator and denominator by xn.

I In our example:

Page 11: Limits at Infinity, Part 1

The Basic Technique For Solving Limits at Infinity

To solve these limits we use a basic technique:

1. First of all, we find the greatest exponent in our function.

I For example:

2. Then we divide both the numerator and denominator by xn.

I In our example:

Page 12: Limits at Infinity, Part 1

The Basic Technique For Solving Limits at Infinity

To solve these limits we use a basic technique:

1. First of all, we find the greatest exponent in our function.I For example:

2. Then we divide both the numerator and denominator by xn.

I In our example:

Page 13: Limits at Infinity, Part 1

The Basic Technique For Solving Limits at Infinity

To solve these limits we use a basic technique:

1. First of all, we find the greatest exponent in our function.I For example:

2x2 − 1

x2 + x

2. Then we divide both the numerator and denominator by xn.

I In our example:

Page 14: Limits at Infinity, Part 1

The Basic Technique For Solving Limits at Infinity

To solve these limits we use a basic technique:

1. First of all, we find the greatest exponent in our function.I For example:

2x2 − 1

x2 + x

The greatest exponent is 2.

2. Then we divide both the numerator and denominator by xn.

I In our example:

Page 15: Limits at Infinity, Part 1

The Basic Technique For Solving Limits at Infinity

To solve these limits we use a basic technique:

1. First of all, we find the greatest exponent in our function.I For example:

2x2 − 1

x2 + x

The greatest exponent is 2.

2. Then we divide both the numerator and denominator by xn.

I In our example:

Page 16: Limits at Infinity, Part 1

The Basic Technique For Solving Limits at Infinity

To solve these limits we use a basic technique:

1. First of all, we find the greatest exponent in our function.I For example:

2x2 − 1

x2 + x

The greatest exponent is 2.

2. Then we divide both the numerator and denominator by xn.Here n is the greatest exponent we found before.

I In our example:

Page 17: Limits at Infinity, Part 1

The Basic Technique For Solving Limits at Infinity

To solve these limits we use a basic technique:

1. First of all, we find the greatest exponent in our function.I For example:

2x2 − 1

x2 + x

The greatest exponent is 2.

2. Then we divide both the numerator and denominator by xn.Here n is the greatest exponent we found before.

I In our example:

Page 18: Limits at Infinity, Part 1

The Basic Technique For Solving Limits at Infinity

To solve these limits we use a basic technique:

1. First of all, we find the greatest exponent in our function.I For example:

2x2 − 1

x2 + x

The greatest exponent is 2.

2. Then we divide both the numerator and denominator by xn.Here n is the greatest exponent we found before.

I In our example:2x2−1x2

x2+xx2

Page 19: Limits at Infinity, Part 1

3. Now we simplify our expression algebraically:

4. Now we calculate the limit directly.

Page 20: Limits at Infinity, Part 1

3. Now we simplify our expression algebraically:

2x2−1x2

x2+xx2

4. Now we calculate the limit directly.

Page 21: Limits at Infinity, Part 1

3. Now we simplify our expression algebraically:

2x2−1x2

x2+xx2

=2x2

x2− 1

x2

x2

x2+ x

x2

4. Now we calculate the limit directly.

Page 22: Limits at Infinity, Part 1

3. Now we simplify our expression algebraically:

2x2−1x2

x2+xx2

=

2��x2

��x2− 1

x2

x2

x2+ x

x2

4. Now we calculate the limit directly.

Page 23: Limits at Infinity, Part 1

3. Now we simplify our expression algebraically:

2x2−1x2

x2+xx2

=

2��x2

��x2− 1

x2

��x2

��x2+ x

x2

4. Now we calculate the limit directly.

Page 24: Limits at Infinity, Part 1

3. Now we simplify our expression algebraically:

2x2−1x2

x2+xx2

=

2��x2

��x2− 1

x2

��x2

��x2+ �x

x �2

4. Now we calculate the limit directly.

Page 25: Limits at Infinity, Part 1

3. Now we simplify our expression algebraically:

2x2−1x2

x2+xx2

=

2��x2

��x2− 1

x2

��x2

��x2+ �x

x �2

=2− 1

x2

1 + 1x

4. Now we calculate the limit directly.

Page 26: Limits at Infinity, Part 1

3. Now we simplify our expression algebraically:

2x2−1x2

x2+xx2

=

2��x2

��x2− 1

x2

��x2

��x2+ �x

x �2

=2− 1

x2

1 + 1x

4. Now we calculate the limit directly.

Page 27: Limits at Infinity, Part 1

The First Example

Let’s find the following limit:

limx→∞

4x3 − 2x2 + 1

5x3 − 3

First of all, we find the greatest exponent there. In this case, it is 3.Next, we divide everything by x3:

Page 28: Limits at Infinity, Part 1

The First Example

Let’s find the following limit:

limx→∞

4x3 − 2x2 + 1

5x3 − 3

First of all, we find the greatest exponent there. In this case, it is 3.

Next, we divide everything by x3:

Page 29: Limits at Infinity, Part 1

The First Example

Let’s find the following limit:

limx→∞

4x3 − 2x2 + 1

5x3 − 3

First of all, we find the greatest exponent there. In this case, it is 3.Next, we divide everything by x3:

Page 30: Limits at Infinity, Part 1

The First Example

Let’s find the following limit:

limx→∞

4x3 − 2x2 + 1

5x3 − 3

First of all, we find the greatest exponent there. In this case, it is 3.Next, we divide everything by x3:

limx→∞

4x3

x3− 2x2

x3+ 1

x3

5x3

x3− 3

x3

Page 31: Limits at Infinity, Part 1

The First Example

Let’s find the following limit:

limx→∞

4x3 − 2x2 + 1

5x3 − 3

First of all, we find the greatest exponent there. In this case, it is 3.Next, we divide everything by x3:

limx→∞

4��x3

��x3− 2x2

x3+ 1

x3

5x3

x3− 3

x3

Page 32: Limits at Infinity, Part 1

The First Example

Let’s find the following limit:

limx→∞

4x3 − 2x2 + 1

5x3 − 3

First of all, we find the greatest exponent there. In this case, it is 3.Next, we divide everything by x3:

limx→∞

4��x3

��x3− 2��x2

x �3+ 1

x3

5x3

x3− 3

x3

Page 33: Limits at Infinity, Part 1

The First Example

Let’s find the following limit:

limx→∞

4x3 − 2x2 + 1

5x3 − 3

First of all, we find the greatest exponent there. In this case, it is 3.Next, we divide everything by x3:

limx→∞

4��x3

��x3− 2��x2

x �3+ 1

x3

5��x3

��x3− 3

x3

Page 34: Limits at Infinity, Part 1

The First Example

Let’s find the following limit:

limx→∞

4x3 − 2x2 + 1

5x3 − 3

First of all, we find the greatest exponent there. In this case, it is 3.Next, we divide everything by x3:

limx→∞

4��x3

��x3− 2��x2

x �3+ 1

x3

5��x3

��x3− 3

x3

And we’re left with:

Page 35: Limits at Infinity, Part 1

The First Example

Let’s find the following limit:

limx→∞

4x3 − 2x2 + 1

5x3 − 3

First of all, we find the greatest exponent there. In this case, it is 3.Next, we divide everything by x3:

limx→∞

4��x3

��x3− 2��x2

x �3+ 1

x3

5��x3

��x3− 3

x3

And we’re left with:

limx→∞

4− 2x + 1

x3

5− 3x3

Page 36: Limits at Infinity, Part 1

The First Example

Now we can calculate the limit directly:

Page 37: Limits at Infinity, Part 1

The First Example

Now we can calculate the limit directly:

limx→∞

4− 2x + 1

x3

5− 3x3

Page 38: Limits at Infinity, Part 1

The First Example

Now we can calculate the limit directly:

limx→∞

4− 2x + 1

x3

5− 3x3

How do we do that?!

Page 39: Limits at Infinity, Part 1

The First Example

Now we can calculate the limit directly:

limx→∞

4− 2x + 1

x3

5− 3x3

How do we do that?!Just observe that anything that is divided by x will go to zero.

Page 40: Limits at Infinity, Part 1

The First Example

Now we can calculate the limit directly:

limx→∞

4− 2x + 1

x3

5− 3x3

How do we do that?!Just observe that anything that is divided by x will go to zero.Why?

Page 41: Limits at Infinity, Part 1

The First Example

Now we can calculate the limit directly:

limx→∞

4− 2x + 1

x3

5− 3x3

How do we do that?!Just observe that anything that is divided by x will go to zero.Why?Because x is approaching ∞!

Page 42: Limits at Infinity, Part 1

The First Example

Now we can calculate the limit directly:

limx→∞

4− 2x + 1

x3

5− 3x3

How do we do that?!Just observe that anything that is divided by x will go to zero.Why?Because x is approaching ∞!Just try with your calculator. Divide anything by a very bignumber and you’ll get very close to 0.

Page 43: Limits at Infinity, Part 1

The First Example

Page 44: Limits at Infinity, Part 1

The First Example

So, using that fact, we have that:

Page 45: Limits at Infinity, Part 1

The First Example

So, using that fact, we have that:

limx→∞

4− 2x + 1

x3

5− 3x3

Page 46: Limits at Infinity, Part 1

The First Example

So, using that fact, we have that:

limx→∞

4−���0

2x + 1

x3

5− 3x3

Page 47: Limits at Infinity, Part 1

The First Example

So, using that fact, we have that:

limx→∞

4−���0

2x +��70

1x3

5− 3x3

Page 48: Limits at Infinity, Part 1

The First Example

So, using that fact, we have that:

limx→∞

4−���0

2x +��70

1x3

5−��70

3x3

Page 49: Limits at Infinity, Part 1

The First Example

So, using that fact, we have that:

limx→∞

4−���0

2x +��70

1x3

5−��70

3x3

And we’re left with:

Page 50: Limits at Infinity, Part 1

The First Example

So, using that fact, we have that:

limx→∞

4−���0

2x +��70

1x3

5−��70

3x3

And we’re left with:

limx→∞

4

5

Page 51: Limits at Infinity, Part 1

The First Example

So, using that fact, we have that:

limx→∞

4−���0

2x +��70

1x3

5−��70

3x3

And we’re left with:

limx→∞

4

5=

4

5

Page 52: Limits at Infinity, Part 1

The First Example

So, using that fact, we have that:

limx→∞

4−���0

2x +��70

1x3

5−��70

3x3

And we’re left with:

limx→∞

4

5=

4

5

That’s the final answer!

Page 53: Limits at Infinity, Part 1