Problem with equation of line tangent to curve

[Chas3down]

Homework Statement

Now use your answer from part (a)(This anwser is f'(25) = 7/10, which is correct) to find the equation of the tangent line to the curve at the point (25, f(25)).

Homework Equations

f(x) = 7*sqrt(x)+3

The Attempt at a Solution

f'(25) = 7/10
f(25) = 38
y=mx+b
38=7/10*25+b

y=7/10x + 41/2

This should be the correct answer... but it won't accept it.


if you want to view the entire problem, http://i.imgur.com/xtVehti.png

 

[Yosty22]

Try using something other than y=mx+b. Do you know any other ways to write the equation that doesn't rely on B?

 

[Chas3down]

Try using something other than y=mx+b. Do you know any other ways to write the equation that doesn't rely on B?

we are given y= ?

so y=mx+b is really the only linear function they could be looking for.

 

[Yosty22]

Try y-y_1=m(x-x_1). You are given y_1 and x_1 (or can easily find them) and you have already solved for m. The rest is plugging in and simplifying.

 

[Chas3down]

Try y-y_1=m(x-x_1). You are given y_1 and x_1 (or can easily find them) and you have already solved for m. The rest is plugging in and simplifying.

edit: i am an idiot... had a - instead of a +