Find the break even points of the expression $16y^2+4y^2-8$

$classify\left(x^2-x^3+1-1\cdot 4\cdot x\right)$

$classify\left(x^2+1-1\cdot 4\cdot x\right)$

$classify\left(x^2-x^3-1\cdot 4\cdot x\right)$

$classify\left(3m^2-2m\cdot n+5n^2\right)$

$classify\left(x^2+1-4\cdot x\right)$

$classify\left(x^2-4\cdot x\right)$

$classify\left(-x^3\cdot y\right)$