A quadratic function can assume this form:
$$ q(x) = x^{T}Gx + x^{T}c $$
Taking that into consideration is this a quadratic function?
$$ 2{x_{1}}^2 + 3x_{1}{x_{2}}^2 + 6{x_{1}^{2}}x_{2} + {x_{2}}^2 + 4x_{1}x_{2} + x_{2}$$
Having ${x_{2}}^2$ and multiplying that by $x_{1}$ makes me unsure