basically, it's an expression where the highest exponent is 2, and the variable with the exponent of 2 has to be in the expression.
your expression is 1/2 (h-6)=0
the highest exponent in your expression is h, which is the same as h^1 which means h raised to the exponent of 1.
that would not be quadratic.
an expression that included h^2 would be quadratic.
sometime the expression might be in the of (h - 6) * h.
while that doesn't, at first glance, look to be quadratic, when you multiply out the factors you will see that it is quadratic because it becomes h^2 - 6h.
the equation of 1/2 (h-6) = 0 becomes 1/2 * h - 3 = 0 when you multiply out the factors.
the highest exponent is 1 which is not quadratic.
to be quadratic, the highest exponent in the expression has to be 2.
