Which function is a quadratic function?

For choice B, distribute and simplify: y − 3x² = 3(x² + 5) + 1 = 3x² + 16. Adding 3x² to both sides gives y = 6x² + 16, which is a quadratic function because its highest power of x is 2. The other choices do not give a quadratic function of x: A has y², C is linear, and D includes an x³ term.

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