Big Ideas Math Algebra 1, 2015
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Big Ideas Math Algebra 1, 2015 View details
3. Solving Radical Equations
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Exercise 7 Page 561

Square both sides of the equation.

8

Practice makes perfect

We want to find and check the solution of the given radical equation.

Finding the Solution

The first step in solving this equation is squaring both sides. Then, once the radicals are gone, we will solve for the variable using the Properties of Equality.
sqrt(3x+1)=sqrt(4x-7)
( sqrt(3x+1) )^2= ( sqrt(4x-7) )^2
3x+1=4x-7
1=x-7
8=x
x=8
The solution of our equation is x= 8.

Checking the Solution

Now, we need to check whether our solution is extraneous. To check our solution, we will substitute 8 for x into the original equation. If we obtain a true statement, the solution is not extraneous. If we obtain a false statement, the solution is extraneous.
sqrt(3x+1)=sqrt(4x-7)
sqrt(3( 8)+1)? =sqrt(4( 8)-7)
sqrt(24+1)? =sqrt(32-7)
sqrt(25)? =sqrt(25)
5=5 âś“
We obtained a true statement, so x=8 is a solution to the equation.

Alternative Solution

Using a Graphing Calculator

Another way to solve this equation is by using a graphing calculator. We will draw separate graphs for each side of the equation and then find the x-value of the point of intersection.

Graphing the Functions

We first press the Y= button and type the function from the left-hand side in one of the rows and the function from the right-hand side in another. Having written functions, we can push GRAPH to draw them.

Intersection Point

Having graphed the functions, we are ready to find the intersection point. By pressing 2ND and then CALC, we can select the option intersect.

Graffönster från TI-82

Then the calculator will ask for the first and second curve as well as a guess. After that, the x-value of the point of intersection should be shown.

Window with a graph

The x-value of the point of intersection is 8. Therefore, as we found algebraically, x=8 is a solution to the given equation.