through wikipedia:In algebra, a quadratic function, a quadratic polynomial, a polynomial of degree 2, or merely a quadratic, is a polynomial function in one or much more variables in i beg your pardon the highest-degree term is that the second degree.

You are watching: A quadratic polynomial has a degree of 2

But the listed below polynomial is also of degree 2 and also non quadratic:

xy + x + y

So, why perform we say, polynomial of level 2 is a quadratic function?

We say it since of conventions. It makes sense.

I think the best reason why is that whether a duty on the airplane is quadratic shouldn"t count on exactly which coordinate axes we impose ~ above the plane. Because that instance, if ns didn"t choose your \$xy\$-axes, and instead wanted \$uv\$-axes \$45^circ\$ to yours (say my allude \$(1,0)\$ is at your \$(1,1)\$ and also my allude \$(0,1)\$ is at your \$(-1,1)\$), climate my expression for the same function would be\$\$frac14u^2-frac14v^2 + u\$\$which clearly has quadratic terms.

\$xy+x+y =0\$ (I added the = 0 to do your question complete) is no of degree two for x.

Rearranging: \$y=frac-xx+1\$

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