The electric potential V is given as a function of distance x (metre) by $V = (5x^2 + 10x – 9) $ volt. Value of electric field at x = 1 is .....
$ E = {-dv \over dx } = { -d \over dx } ( 5 x^2 + 10x -9 ) = -10x -10 $ $ \therefore E_(x-1) = - 10 \times 1 -10 = -20 { v \over m} $