limits by rationalization

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We solve limits by rationalizing. This is the second technique you may learn after limits by factoring. We solve two examples step by step. Watch video: http://www.youtube.com/watch?v=8CtpuojMJzA More videos and lessons: http://www.intuitive-calculus.com/solving-limits.html

TRANSCRIPT

Example 1

Example 1

Let’s try to find the limit:

Example 1

Let’s try to find the limit:

limh→0

√a + h −

√a

h

Example 1

Let’s try to find the limit:

limh→0

√a + h −

√a

h

We rationalize the expression.

Example 1

Let’s try to find the limit:

limh→0

√a + h −

√a

h

We rationalize the expression.In this case by multiplying and dividing by the conjugate.

Example 1

Let’s try to find the limit:

limh→0

√a + h −

√a

h

We rationalize the expression.In this case by multiplying and dividing by the conjugate.

limh→0

√a + h −

√a

h=

Example 1

Let’s try to find the limit:

limh→0

√a + h −

√a

h

We rationalize the expression.In this case by multiplying and dividing by the conjugate.

limh→0

√a + h −

√a

h= lim

h→0

Example 1

Let’s try to find the limit:

limh→0

√a + h −

√a

h

We rationalize the expression.In this case by multiplying and dividing by the conjugate.

limh→0

√a + h −

√a

h= lim

h→0

√a + h −

√a

h.

Example 1

Let’s try to find the limit:

limh→0

√a + h −

√a

h

We rationalize the expression.In this case by multiplying and dividing by the conjugate.

limh→0

√a + h −

√a

h= lim

h→0

√a + h −

√a

h.

√a + h +

√a√

a + h +√a

Example 1

Let’s try to find the limit:

limh→0

√a + h −

√a

h

We rationalize the expression.In this case by multiplying and dividing by the conjugate.

limh→0

√a + h −

√a

h= lim

h→0

√a + h −

√a

h.���

����*1√

a + h +√a√

a + h +√a

Example 1

Let’s try to find the limit:

limh→0

√a + h −

√a

h

We rationalize the expression.In this case by multiplying and dividing by the conjugate.

limh→0

√a + h −

√a

h= lim

h→0

√a + h −

√a

h.

√a + h +

√a√

a + h +√a

Example 1

Let’s try to find the limit:

limh→0

√a + h −

√a

h

We rationalize the expression.In this case by multiplying and dividing by the conjugate.

limh→0

√a + h −

√a

h= lim

h→0

√a + h −

√a

h.

√a + h +

√a√

a + h +√a

= limh→0

(√a + h

)2 − (√a)2

h(√

a + h +√a)

Example 1

Let’s try to find the limit:

limh→0

√a + h −

√a

h

We rationalize the expression.In this case by multiplying and dividing by the conjugate.

limh→0

√a + h −

√a

h= lim

h→0

√a + h −

√a

h.

√a + h +

√a√

a + h +√a

= limh→0

(√a + h

)2 − (√a)2

h(√

a + h +√a) = lim

h→0

a + h − a

h(√

a + h +√a)

Example 1

Let’s try to find the limit:

limh→0

√a + h −

√a

h

We rationalize the expression.In this case by multiplying and dividing by the conjugate.

limh→0

√a + h −

√a

h= lim

h→0

√a + h −

√a

h.

√a + h +

√a√

a + h +√a

= limh→0

(√a + h

)2 − (√a)2

h(√

a + h +√a) = lim

h→0

�a + h − �ah(√

a + h +√a)

Example 1

Let’s try to find the limit:

limh→0

√a + h −

√a

h

We rationalize the expression.In this case by multiplying and dividing by the conjugate.

limh→0

√a + h −

√a

h= lim

h→0

√a + h −

√a

h.

√a + h +

√a√

a + h +√a

= limh→0

(√a + h

)2 − (√a)2

h(√

a + h +√a) = lim

h→0

�a + h − �ah(√

a + h +√a)

= limh→0

h

h(√

a + h +√a)

Example 1

Let’s try to find the limit:

limh→0

√a + h −

√a

h

We rationalize the expression.In this case by multiplying and dividing by the conjugate.

limh→0

√a + h −

√a

h= lim

h→0

√a + h −

√a

h.

√a + h +

√a√

a + h +√a

= limh→0

(√a + h

)2 − (√a)2

h(√

a + h +√a) = lim

h→0

�a + h − �ah(√

a + h +√a)

= limh→0

�h

�h(√

a + h +√a)

Example 1

Let’s try to find the limit:

limh→0

√a + h −

√a

h

We rationalize the expression.In this case by multiplying and dividing by the conjugate.

limh→0

√a + h −

√a

h= lim

h→0

√a + h −

√a

h.

√a + h +

√a√

a + h +√a

= limh→0

(√a + h

)2 − (√a)2

h(√

a + h +√a) = lim

h→0

�a + h − �ah(√

a + h +√a)

= limh→0

�h

�h(√

a + h +√a) = lim

h→0

1√a + h +

√a

Example 1

Let’s try to find the limit:

limh→0

√a + h −

√a

h

We rationalize the expression.In this case by multiplying and dividing by the conjugate.

limh→0

√a + h −

√a

h= lim

h→0

√a + h −

√a

h.

√a + h +

√a√

a + h +√a

= limh→0

(√a + h

)2 − (√a)2

h(√

a + h +√a) = lim

h→0

�a + h − �ah(√

a + h +√a)

= limh→0

�h

�h(√

a + h +√a) = lim

h→0

1

����:

√a√

a + h +√a

Example 1

Let’s try to find the limit:

limh→0

√a + h −

√a

h

We rationalize the expression.In this case by multiplying and dividing by the conjugate.

limh→0

√a + h −

√a

h= lim

h→0

√a + h −

√a

h.

√a + h +

√a√

a + h +√a

= limh→0

(√a + h

)2 − (√a)2

h(√

a + h +√a) = lim

h→0

�a + h − �ah(√

a + h +√a)

= limh→0

�h

�h(√

a + h +√a) = lim

h→0

1

����:

√a√

a + h +√a

=1

2√a

Example 1

Let’s try to find the limit:

limh→0

√a + h −

√a

h

We rationalize the expression.In this case by multiplying and dividing by the conjugate.

limh→0

√a + h −

√a

h= lim

h→0

√a + h −

√a

h.

√a + h +

√a√

a + h +√a

= limh→0

(√a + h

)2 − (√a)2

h(√

a + h +√a) = lim

h→0

�a + h − �ah(√

a + h +√a)

= limh→0

�h

�h(√

a + h +√a) = lim

h→0

1

����:

√a√

a + h +√a

=1

2√a

Example 2

Example 2

limx→0

√1 + x − 1

x

Example 2

limx→0

√1 + x − 1

x

We rationalize using the same method.

Example 2

limx→0

√1 + x − 1

x

We rationalize using the same method.

limx→0

√1 + x − 1

x=

Example 2

limx→0

√1 + x − 1

x

We rationalize using the same method.

limx→0

√1 + x − 1

x= lim

x→0

√1 + x − 1

x.

Example 2

limx→0

√1 + x − 1

x

We rationalize using the same method.

limx→0

√1 + x − 1

x= lim

x→0

√1 + x − 1

x.

√1 + x + 1√1 + x + 1

Example 2

limx→0

√1 + x − 1

x

We rationalize using the same method.

limx→0

√1 + x − 1

x= lim

x→0

√1 + x − 1

x.��

�����*1√

1 + x + 1√1 + x + 1

Example 2

limx→0

√1 + x − 1

x

We rationalize using the same method.

limx→0

√1 + x − 1

x= lim

x→0

√1 + x − 1

x.

√1 + x + 1√1 + x + 1

Example 2

limx→0

√1 + x − 1

x

We rationalize using the same method.

limx→0

√1 + x − 1

x= lim

x→0

√1 + x − 1

x.

√1 + x + 1√1 + x + 1

= limx→0

(√1 + x

)2 − 12

x(√

1 + x + 1)

Example 2

limx→0

√1 + x − 1

x

We rationalize using the same method.

limx→0

√1 + x − 1

x= lim

x→0

√1 + x − 1

x.

√1 + x + 1√1 + x + 1

= limx→0

(√1 + x

)2 − 12

x(√

1 + x + 1) = lim

x→0

1 + x − 1

x(√

1 + x + 1)

Example 2

limx→0

√1 + x − 1

x

We rationalize using the same method.

limx→0

√1 + x − 1

x= lim

x→0

√1 + x − 1

x.

√1 + x + 1√1 + x + 1

= limx→0

(√1 + x

)2 − 12

x(√

1 + x + 1) = lim

x→0

�1 + x − �1x(√

1 + x + 1)

Example 2

limx→0

√1 + x − 1

x

We rationalize using the same method.

limx→0

√1 + x − 1

x= lim

x→0

√1 + x − 1

x.

√1 + x + 1√1 + x + 1

= limx→0

(√1 + x

)2 − 12

x(√

1 + x + 1) = lim

x→0

�1 + x − �1x(√

1 + x + 1)

= limx→0

x

x(√

1 + x + 1)

Example 2

limx→0

√1 + x − 1

x

We rationalize using the same method.

limx→0

√1 + x − 1

x= lim

x→0

√1 + x − 1

x.

√1 + x + 1√1 + x + 1

= limx→0

(√1 + x

)2 − 12

x(√

1 + x + 1) = lim

x→0

�1 + x − �1x(√

1 + x + 1)

= limx→0

�x

�x(√

1 + x + 1)

Example 2

limx→0

√1 + x − 1

x

We rationalize using the same method.

limx→0

√1 + x − 1

x= lim

x→0

√1 + x − 1

x.

√1 + x + 1√1 + x + 1

= limx→0

(√1 + x

)2 − 12

x(√

1 + x + 1) = lim

x→0

�1 + x − �1x(√

1 + x + 1)

= limx→0

�x

�x(√

1 + x + 1) = lim

x→0

1√1 + x + 1

Example 2

limx→0

√1 + x − 1

x

We rationalize using the same method.

limx→0

√1 + x − 1

x= lim

x→0

√1 + x − 1

x.

√1 + x + 1√1 + x + 1

= limx→0

(√1 + x

)2 − 12

x(√

1 + x + 1) = lim

x→0

�1 + x − �1x(√

1 + x + 1)

= limx→0

�x

�x(√

1 + x + 1) = lim

x→0

1

�����:

√1√

1 + x + 1

Example 2

limx→0

√1 + x − 1

x

We rationalize using the same method.

limx→0

√1 + x − 1

x= lim

x→0

√1 + x − 1

x.

√1 + x + 1√1 + x + 1

= limx→0

(√1 + x

)2 − 12

x(√

1 + x + 1) = lim

x→0

�1 + x − �1x(√

1 + x + 1)

= limx→0

�x

�x(√

1 + x + 1) = lim

x→0

1

�����:

√1√

1 + x + 1

=1

2

Example 2

limx→0

√1 + x − 1

x

We rationalize using the same method.

limx→0

√1 + x − 1

x= lim

x→0

√1 + x − 1

x.

√1 + x + 1√1 + x + 1

= limx→0

(√1 + x

)2 − 12

x(√

1 + x + 1) = lim

x→0

�1 + x − �1x(√

1 + x + 1)

= limx→0

�x

�x(√

1 + x + 1) = lim

x→0

1

�����:

√1√

1 + x + 1

=1

2

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