View source for Quasi-linear equation

A partial differential equation (cf. [[Differential equation, partial|Differential equation, partial]]) that is linear with respect to the leading derivatives of the unknown function. For example, the equation

<table class="eq" style="width:100%;"> <tr><td valign="top" style="width:94%;text-align:center;"><img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/q/q076/q076570/q0765701.png" /></td> </tr></table>

is a second-order quasi-linear equation with respect to the unknown function <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/q/q076/q076570/q0765702.png" />.

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====References====
<table><TR><TD valign="top">[a1]</TD> <TD valign="top">  H.M. Luberstein,   "Theory of partial differential equations" , Acad. Press  (1972)  pp. 10; 12; 27</TD></TR><TR><TD valign="top">[a2]</TD> <TD valign="top">  G.F. Carrier,   C.E. Pearson,   "Partial differential equations" , Acad. Press  (1976)  pp. Sect. 6.3; 89; 252</TD></TR></table>