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# The electric potential as a function of distance x is given by $V= (-5x ^2-10 x +9) \;volt$ . The electric field at point $(1,2)$ is

$(A)\;20v/m \\ (B)\;-20 v/m \\ (C)\; 24 v/m \\ (D)\;-24 v/m$

$E= \large\frac{-dv}{dx}$
$\quad= 10 x +10$
$E(at X=1)=20 v/m$
Hence A is the correct answer.