Advanced MathEasySum of x-coordinates of symmetric solutions
Advanced Math practice question
The system y = x² and y = 9 has two solutions. What is the sum of the x-coordinates of the two solutions?
Answer: 0
x² = 9 gives x = 3 and x = −3, whose sum is 0.
Common wrong answers
- If you answered 3
- 3 is only one of the x-coordinates.
- If you answered 6
- 6 counts 3 twice, forgetting the negative solution.
- If you answered 18
- 18 adds the y-coordinates.
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