Pearson Algebra 1 Common Core, 2011
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Pearson Algebra 1 Common Core, 2011 View details
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Exercise 20 Page 661

Raise both sides of the equation to a power equal to the index of the radical.

4

Practice makes perfect

To solve equations with a variable expression inside a radical, we first want to make sure the radical is isolated. Then we can raise both sides of the equation to a power equal to the index of the radical. Let's try to solve our equation using this method!

sqrt(x)+2=x
sqrt(x)=x-2
(sqrt(x))^2=(x-2)^2
x=(x-2)^2
â–¼
(a-b)^2=a^2-2ab+b^2

Evaluate

x=x^2-2(x)(2)+2^2
x=x^2-4x+2^2
x = x^2-4x+4
0 = x^2-4x+4-x
0 = x^2-5x+4
x^2-5x+4=0

We now have a quadratic equation, and we need to find its roots. To do it, let's identify the values of a, b, and c. x^2 -5x +4 = 0 ⇕ 1x^2+( -5)x+ 4=0

We can see that a= 1, b= -5, and c= 4. Let's substitute these values into the Quadratic Formula.

x=- b±sqrt(b^2-4ac)/2a
x=- ( -5)±sqrt(( -5)^2-4( 1)( 4))/2( 1)
â–¼
Solve for x and Simplify
x=5±sqrt((-5)^2-4(1)(4))/2(1)
x=5±sqrt(5^2-4(1)(4))/2(1)
x=5±sqrt(25-4(1)(4))/2(1)
x=5±sqrt(25-16)/2
x=5±sqrt(9)/2
x=5± 3/2

Using the Quadratic Formula, we found that the solutions of the given equation are x= 5± 32.

x=5± 3/2
x_1=5+3/2 x_2=5-3/2
x_1=8/2 x_2=2/2
x_1= 4 x_2= 1

Therefore, the solutions are x_1= 4 and x_2= 1. Let's check them to see if we have any extraneous solutions.

Checking the Solutions

We will check x_1=4 and x_2=1 one at a time.

x_1=4

Let's substitute x=4 into the original equation.

sqrt(x)+2=x
sqrt(4)+2? = 4
2+2? =4
4=4 ✓

We got a true statement. Therefore, x=4 is a solution of the original equation.

x_2=1

Now, let's substitute x=1.

sqrt(x)+2=x
sqrt(1)+2? = 1
1+2? =1
3 ≠ 1 *

In this case, we got a false statement, so x=1 is an extraneous solution. Therefore, x=4 is the only solution of the original equation.