16Hit1600
AlgebraVery hardCondition for an equation to have no solution

Algebra practice question

The equation 5x + 3 = 5x + c, where c is a constant, has no solution. Which of the following must be true?

  1. A. c ≠ 3Correct
  2. B. c = 3
  3. C. c = 0
  4. D. c = 5

Answer: A. c ≠ 3

The x-terms cancel, leaving 3 = c. If c is anything other than 3 the statement is false for every x; if c = 3 every x works.

Why the other answers are wrong

B. c = 3
c = 3 gives infinitely many solutions.
C. c = 0
c = 0 works, but so does every value except 3.
D. c = 5
c = 5 works, but so does every value except 3.

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