Use linear approximation, i.e. the tangent line, to approximate 8.4^(1/3) as follows:

Question

Use linear approximation, i.e. the tangent line, to approximate 8.4^(1/3)  as follows: 
Let f(x)= x^(1/3) . The equation of the tangent line to f(x)  at x=8  can be written in the form y=mx+c  where m=1/12 and c=4/3: 
Using this, find our approximation for  8.4^(1/3).