The function is .

               (Apply derivative with respect to x)

            (The sum rule)

            (The power rule:)

To find the slope at point (1, 2)

 So,                         (Substitute x = 1 and  y = 2)

To find the tangent line use point-slope form:

                       (Point-slope form)

                        (Substitute x = 1, m = and  y = 2)

Therefore the tangent line is .