Which function is a quadratic function?

A quadratic function has highest power of x equal to 2 after simplifying. In choice D, h(x) = 3x(x − 2) − 4 = 3x² − 6x − 4, so its highest power is 2. The other choices simplify to functions of degree 3, degree 4, and degree 1, respectively. Therefore, h(x) = 3x(x − 2) − 4 is the quadratic function.

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