Question

y= 30.6xt-218.0 linear or quadratic

Answer 1

But what is t?? is it a variable or some kind of parameter?

If it's a variable, then I don't think that equation is EITHER linear or quadratic?

If it's a typo, then what @AkashdeepDeb said... lol.

Answer 2

it is quadratic ,power of xt is 1+1=2 so.

Answer 3

I really don't think so.

A quadratic function is a polynomial function of the form:

\(\Large f(x)=ax^2+bx+c, ~a\neq0\)

That's a pretty standard definition. I've never seen "quadratic" defined as any 2nd-degree multivariate equation.