Pearson Algebra 1 Common Core, 2011
PA
Pearson Algebra 1 Common Core, 2011 View details
4. Solving Radical Equations
Continue to next subchapter

Exercise 46 Page 637

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

1,6

Practice makes perfect

For simplicity, we will start by replacing the variable a with the variable x. a=sqrt(7a-6) a= x ⟶ x=sqrt(7 x-6) Since the radical is isolated, 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!

x=sqrt(7x-6)
x^2=(sqrt(7x-6))^2
x^2 =7x-6
â–¼
LHS-(7x-6)=RHS-(7x-6)
x^2-7x=-6
x^2-7x+6=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 -7x +6 = 0 ⇔ 1x^2+( - 7)x+ 6=0 We can see that a= 1, b= - 7, and c= 6. Let's substitute these values into the Quadratic Formula.

x=- b±sqrt(b^2-4ac)/2a
x=- ( -7)±sqrt(( - 7)^2-4( 1)( 6))/2( 1)
â–¼
Evaluate right-hand side
x=7±sqrt((- 7)^2-4(1)(6))/2(1)
x=7±sqrt(49-4(1)(6))/2(1)
x=7±sqrt(49-24)/2
x=7±sqrt(25)/2
x=7± 5/2

Using the Quadratic Formula, we found that the solutions of the given equation are x= 7± 5 2.

x=7± 5/2
x_1=7+5/2 x_2=7-5/2
x_1=12/2 x_2=2/2
x_1= 6 x_2= 1

Therefore, the solutions are x_1= 6 and x_2= 1. Recall that, at the beginning of the solution, we substituted x for a. Therefore, the solutions to the original equation are a_1= 6 and a_2= 1. Let's check them to see if we have any extraneous solutions.

Checking the Solutions

We will check a_1=6 and a_2=1 one at a time.

a_1=6

Let's substitute a= 6.

a=sqrt(7a-6)
6? =sqrt(7( 6)-6)
â–¼
Simplify
6? =sqrt(42-6)
6? =sqrt(36)
6= 6 ✓

In this case we got a true statement. Therefore, a=6 is a solution of the original equation.

a_1=1

Let's now substitute a= 1 into the original equation.

a=sqrt(7a-6)
1? =sqrt(7( 1)-6)
â–¼
Simplify
1? =sqrt(7-6)
1? =sqrt(1)
1= 1 ✓

We got a true statement, so a=1 is not an extraneous solution. Therefore, the equation has two solutions which are 6 and 1.