Find the equation of normal line to the curve y = x3 + 2x + 6 which is parallel to the line x + 14y + 4 = 0.

finding the slope of the tangent by differentiating the curve



m(tangent) = 3x2 + 2


normal is perpendicular to tangent so, m1m2 = – 1


m(normal) =


equation of normal is given by y – y1 = m(normal)(x – x1)


now comparing the slope of normal with the given equation


m(normal) =



x = 2 or – 2


hence the corresponding value of y is 18 or – 6


so, equations of normal are



Or



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