I was reading A. Adrian Albert's Modern Higher Algebra (1938). On p.30, there is such an exercise (emphasis mine):
Let $\mathfrak F$ be a field of characteristic $2$ and $x^2+ax+b=0$ be a quadratic equation with coefficients $a\ne0$ and $b$ in $\mathfrak F$. Show that a linear transformation $x=cy+d$ with coefficients in $\mathfrak F$ cannot carry our quadratic into a reduced quadratic in $y$. But this can be done when $\mathfrak F$ does not have characteristic two.
What does the phrase in bold mean?
This most likely means that a linear transformation cannot produce a quadratic with no linear term over a field of characteristic $2$, but that it can if the field has a different characteristic.