A linear function can be represented in the form \(y = mx + b\), where \(m\) and \(b\) are constants, and the graph of the function is a straight line.
Let's analyze the given options:
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\(y = 2x^3 + 4\): This is a cubic function, not linear.
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\(2y - 5x = 9\): This can be rearranged into the form \(y = \frac{5}{2}x + \frac{9}{2}\), which is linear.
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\(y = -12x + 78, x \neq 0\): This is already in the linear form \(y = mx + b\), where \(m = -12\) and \(b = 78\).
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\(x^2 + y = 33\): Rearranging gives \(y = 33 - x^2\), which is a quadratic function and not linear.
So, the options that are linear functions are \(2y - 5x = 9\) and \(y = -12x + 78\).