16Hit1600
Advanced MathVery hardSum of inputs with a shared output

Advanced Math practice question

The function g is defined by g(x) = 2(x − 4)² − 3. Two different values of x give g(x) = 15. What is the sum of those two values?

Answer: 8

The graph is symmetric about x = 4, so the two inputs average 4 and sum to 8.

Common wrong answers

If you answered 4
4 is the axis of symmetry, half the sum.
If you answered 6
6 is the difference of the inputs.
If you answered 15
15 is the output.

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