英文的导数题Letf(x)=8x+20/(x^2).Thentheequationofthetangentlinetothegraphoff(x)atthepoint(2,21)isgivenbyY=mx+bform=?b=?

Question

英文的导数题
Let f(x)=8x+20/(x^2).Then the equation of the tangent line to the graph of f(x) at the point(2,21) is given by Y=mx+b for m=?b=?

Answer 1

给出的那个点的坐标(2,21)都是多余的,给其中一个坐标就行了
f'(x)=8-40/(x^3)
so
f'(2)=3,
m=3
and the equation of the tangent line can be as below:
y-21=3(x-2)
solve it:
y=3x+15
so
b=15
题目我能看懂,但是如何用英语表达解题步骤,还想请教请教你.