Big Ideas Math Algebra 2, 2014
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Big Ideas Math Algebra 2, 2014 View details
4. Solving Radical Equations and Inequalities
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Exercise 31 Page 266

Raise each side of the equation to the reciprocal of the rational exponent.

x=3

Practice makes perfect
To solve equations with a variable expression raised to a rational exponent, we raise each side of the equation to the reciprocal of the rational exponent. x^(m n)=k ⇔ (x^(m n))^() n m=k^() n m Remember, if m is even, then (x^(m n))^() n m=|x|. In this case m= 1, so we do not need to worry about this. In the given equation the variable term is already isolated, so we will raise each side of the equation to the power of 2.
(x+6)^(12)=x
((x+6)^(12))^2=x^2
â–¼
Simplify
x+6=x^2
6=x^2-x
0=x^2-x-6
x^2-x-6=0
We obtained a quadratic equation. There are many ways to solve a quadratic equation. We will use the Quadratic Formula to solve the equation. Let's determine a, b, and c. x^2-x-6=0 ⇔ 1x^2+( - 1)x+( - 6)=0 We see above that a= 1, b= - 1, and c= - 6. Let's substitute these values into the Quadratic Formula to solve the equation.
x=- b±sqrt(b^2-4ac)/2a
x=-( - 1)±sqrt(( - 1)^2-4( 1)( - 6))/2( 1)
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Simplify right-hand side
x=-(- 1)±sqrt(1-4(1)(- 6))/2(1)
x=1±sqrt(1-4(1)(- 6))/2(1)
x=1±sqrt(1+24)/2
x=1±sqrt(25)/2
x=1± 5/2
Now we can calculate the first root using the positive sign and the second root using the negative sign.
x=1± 5/2
x=1-5/2 x=1+5/2
x=- 2 x=3

Checking the Solutions

Next, we will check the solutions by substituting - 2 and 3 for x into the original equation. If the substitution produces a true statement, we know that our answer is correct. If it does not, then it is an extraneous solution. Let's first check the - 2.
(x+6)^(12)=x
( - 2+6)^(12)? = - 2
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Simplify
4^(12)? =- 2
(2^2)^(12)? =- 2
2≠ - 2 *
Because our substitution produced a false statement, we know that our answer, x=- 2, is not correct. Let's check now the 3.
(x+6)^(12)=x
( 3+6)^(12)? = 3
â–¼
Simplify
9^(12)? =3
(3^2)^(12)? =3
3= 3 ✓
Because our substitution produced a true statement, we know that our answer, x=3, is correct.