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Solve the radical equation the square root of (x + 6) equal to x.
AOnly x = -2 works
BBoth 3 and -2 work
CNeither value works
DOnly x = 3 works
Answer & Solution
Correct answer: D. Only x = 3 works
1. The radical is already alone on the left, so square both sides.
2. Squaring gives x plus 6 equal to x squared.
3. Rearranging gives x squared minus x minus 6 equal to 0.
4. Factoring gives the brackets (x minus 3) and (x plus 2).
5. So the proposed solutions are x equal to 3 and x equal to negative 2.
6. Test x equal to 3: the square root of 9 is 3, which matches the right side.
7. Test x equal to negative 2: the square root of 4 is 2, but the right side is negative 2, so it fails.
8. Squaring both sides created that second root, so it is extraneous and only x equal to 3 survives.
9. Keeping both values skips the check that squaring makes necessary.
10. Rejecting both values ignores that x equal to 3 does satisfy the original equation.
_Source: OpenStax College Algebra (CC BY 4.0), section 2.6 Other Types of Equations_