# Given a Horizontal Derivative Kernel What Would Be the Output Image?

Hi, im solving this problem and everything went well until i went and solved the position p(5,3) and i got the answer of 0. However, the solution guide lists the solution as 150 which is pointed at in blue. I don't understand this since the pixel at the location is 0, meaning we don't have to calculate the solution however the solution says otherwise. Thanks for your time.

d(3,5) = value_at(4,5) - value_at(2,5)