3.07 Radical Equations
Intermediate
Algebra: One Step at a Time. Page
289- 297: #20, 24, 26, 27, 32, 33, 34, 35, 36, 40
NEW
PROBLEMS: #20, 24, 26, 27, 32, 33, 34, 35, 36, 40
Dr. Robert J. Rapalje
Seminole State College of Florida
Sanford, FL 32773
20.

The first step in solving radical equations is to
isolate the radical. In this case, the radical is alone on the left side of
the equation, so it is already isolated. You may proceed by squaring both
sides, in order to “undo” the radical.

On the left side, when you square the square root, you
simply remove the radical sign. On the right side, remember that you are
squaring a binomial, which is the first squared, twice the product, and the
last squared:

At first, it looks like a quadratic equation, but
subtract
from each side, and the
term
subtracts out leaving

To solve for x, add
+4x
to
each side, and subtract 7 from each side, to get the x terms
on the left side, and the number terms on the right side:


x = -3
Since you squared both sides, the answer is NOT
guaranteed. You must check the answers:
Check: 
x = -3



It checks!
24.

Since the radical term is isolated on the right side of
the equation, you may proceed by squaring both sides, in order to “undo” the
radical.

On the left side, when you square the square root, you
simply remove the radical sign. On the right side, remember that you are
squaring a binomial, which is the first squared, twice the product, and the
last squared:

This one is a quadratic equation, so you must set it
equal to zero by subtracting
and
from each side:



Factor the right side of the equation, beginning by
factoring out the common factor of 2:



Since you squared both sides, the answers are NOT
guaranteed. You must check the answers:
Check: 




It checks!
Check: 




Reject this answer!!
The final answer is

26.

It’s a
good idea to begin by multiplying both sides of the equation by the
denominator which is
in
order to clear the fractions.


Since the
radical term is isolated on the right side of the equation, you may proceed
by squaring both sides, in order to “undo” the radical.

On the
left side, when you square the square root, you simply remove the radical
sign. On the right side, remember that you are squaring a binomial, which
is the first squared, twice the product, and the last squared:


This is a
quadratic equation, so you must set it equal to zero:


Factor the
right side of the equation by taking out the common factor of
:

Since you
squared both sides, the answers are NOT guaranteed. You must check the
answers:
Check:


It
checks!
Check: 


It
also checks!!
Final
Answer: 
27.

It’s a
good idea to begin by multiplying both sides of the equation by the
denominator which is
in order to clear the fractions.


Since the
radical term is isolated on the right side of the equation, you may proceed
by squaring both sides, in order to “undo” the radical.

On the
left side, when you square the square root, you simply remove the radical
sign. On the right side, remember that you are squaring a binomial, which
is the first squared, twice the product, and the last squared:


This is a
quadratic equation, so you must set it equal to zero by subtracting
and
from each side:



Factor the
right side of the equation:

Since you
squared both sides, the answers are NOT guaranteed. You must check the
answers:
Check:


It checks!
Check:



It also checks!!
Final Answer:

32.

You must first isolate one of the radicals on the left side. Try adding
.
Now, you can write this:

and square both sides
of the equation in order to eliminate the radical on the left side:
On the left side, you
just remove the square root sign. On the right side, square the first, take
twice the product, and square the second.

Isolate the radical on the right side by adding
and
to
each side:

Since there is a common
factor, divide both sides by 8.

Now, square both sides
again to eliminate the second radical.

This answer still must
be checked in the original equation:



This
checks!
The final answer is

33.

You can
square both sides of the equation in order to eliminate the radical on the
left side:
On the
left side, you just remove the square root sign. On the right side, square
the first, take twice the product, and square the second.

Isolate
the radical on the right side by adding
and
to
each side:

Since
there is a common factor, divide both sides by 2.

Now,
square both sides again to eliminate the second radical.

Set equal
to zero:

Solve the
quadratic equation, by factoring the common factor of x:


These
answers still must be checked in the original equation:
Check x =
0: 


This
checks!!
Check x = 3: 


This
also checks!!
The
final answer is

34.

The first
step is to isolate one of the radicals by adding
to each side:

Now, you
can square both sides of the equation in order to eliminate the radical on
the left side:
On the
left side, you just remove the square root sign. On the right side, square
the first, take twice the product, and square the second.

Isolate
the radical on the right side by adding
and
to each side:

Since
there is a common factor, divide both sides by 4.

Now,
square both sides again to eliminate the second radical.

Set equal
to zero:

Solve the
quadratic equation, by factoring:


These
answers still must be checked in the original equation:



This checks!!



This one does NOT check.
The final
answer is 
35.

This is an
interesting problem! In my first attempts to solve this problem, I tried to
isolate the
by adding
to each side. This solution can be seen on page 305 of
my Intermediate Algebra book. However, I don’t know why, but it turns out
to be an easier solution if you isolate the
by subtracting
from each side.

You may
proceed by squaring both sides, in order to “undo” the radical on the left
side.

Of course
when you square the left side, you must square the negative, which is a
positive, and remove the radical sign. On the right side, remember that you
are squaring a binomial, which is the quantity times itself.


Subtract
and
from each side to isolate the other radical, and you have

Now,
square both sides of the racial.






Since you
squared both sides, the answers are NOT guaranteed. You must check the
answers:
Check:

x
= 0 

It
does NOT check!
x
= 8 

It
does NOT check!
Final Answer: NO SOLUTION!!
36.

The first
step is to isolate one of the radicals by subtracting
from each side of the equation.

Next,
square both sides of the equation in order to eliminate the radical on the
left side:
On the
left side, you just remove the square root sign. On the right side, square
the first, take twice the product, and square the second.

Now, you
must isolate the radical on the right side by adding
and
to each side

Now,
square both sides again to eliminate the second radical.


Set equal
to zero by subtracting
from each side:

Of course
it factors! In this case, take out the common factor of
:


These
answers still must be checked.

Check:



It checks!!
Check:



It does NOT check!!
The final
answer is 
40.

The first
step is to square both sides of the equation in order to eliminate the
radical on the left side:
On the
left side, you just remove the square root sign. On the right side, square
the first, take twice the product, and square the second.


Isolate the radical on the right side by adding +6x and − 26 to each
side:

Since
there is a common factor, divide both sides by 2.

Now,
square both sides again to eliminate the second radical.


Set equal
to zero by adding
to each side:


Solve the
quadratic equation! You can use factoring, the calculator program “POLYSMLT”,
or the quadratic formula! By factoring, it looks like this. It’s a
trinomial, so start by taking out the common factor of 2:



These
answers still must be checked, and it turns out that the
does NOT check. However, the
DOES check, since
.


The final
answer is
.
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