3x^2 - 4 = 7x is the standard form. To get standard form into quadratic you must have one side of the equation equal zero. The easiest way to so is subtracting 7x on both sides of the equation.
3x^2 - 4 = 7x
-7x -7x
3x^2 -7x - 4 = 0
So, 3x^2 -7x - 4 = 0 is the quadratic form.
