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Advanced Math / Nonlinear equations in one variable and systems of equations in two variables Difficulty: Medium

x+9x-9x+9=7

What is the solution to the given equation?

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Explanation

Choice C is correct. Since the left-hand side of the given equation has a factor of x + 9 in both the numerator and the denominator, the solution to the given equation can be found by solving the equation x - 9 = 7 . Adding 9 to both sides of this equation yields x = 16 . Substituting 16 for x in the given equation yields 16+916-916+9=7, or 7=7. Therefore, the solution to the given equation is 16 .

Choice A is incorrect. Substituting 7 for x in the given equation yields 7+97-97+9=7, or -2=7, which is false.

Choice B is incorrect. Substituting 9 for x in the given equation yields 9+99-99+9=7, or 0=7, which is false.

Choice D is incorrect. Substituting 63 for x in the given equation yields 63+963-963+9=7, or 54=7, which is false.