Question 275553
It's a matter of semantics.
quadratic is 2nd order, or exponent 2.  It comes from quadrangle, which is rectangular.
---------------
But, as the other tutor pointed out, it can be a quadratic in x^4, which gives and exponent of 8.
If the exponents are in order as in his example, 8, 4, 0, then it's a quadratic in x^4.  It's {{{a(x^4)^2 + b(x^4)^1 + c(x^4)^0 = 0}}}
-------------
I don't know where you might have gotten the info about exponent 6.