Answer:

and x=4
Step-by-step explanation:
We are given that a curve

We have to find the equation of tangent at point (4,2) on the given curve.
Let y=f(x)
Differentiate w.r.t x

By using the formula 
Substitute x=4
Slope of tangent

In given question


By comparing we get a=4
Point-slope form

Using the formula
The equation of tangent at point (4,2)




83 hope it helps get a good grade
The answer should be -3, I can explain it if you want.
i got 5.14cm i don´t know how much you are supposed to round though
36/42= 0.857142857 x 6=5.142857143