You need to evaluate y', hence, you should differentiate the function with respect to x such that:
`(1/y)*y' = 4x - 1`
`y' = (4x - 1)*y`
You need to evaluate y' at the point (2,1) such that:
`y' = (4*2 - 1)*1`
`y' = 7`
Hence, evaluating y' for `ln y = 2x^2 -x` , at the point (2,1), yields `y' = 7` .