Posted by **maura** on Friday, September 14, 2012 at 3:24pm.

To find the equation of a line, we need the slope of the line and a point on the line.

Since we are requested to find the equation of the tangent line at the point (64, 8), we know that (64, 8) is a point on the line. So we just need to find its slope.

The slope of a tangent line to f(x) at x = a can be found using the formula

mtan = lim x→a f(x) − f(a)/x − a

In this situation, the function is

f(x) = a=

- calculus - eh? -
**Steve**, Friday, September 14, 2012 at 3:29pm
so far, so good. What's the question?

- calculus -
**maura**, Friday, September 14, 2012 at 3:31pm
its asking for f(x) and a

im just trying to figure out how i would go about doing this. thanks for answering me.

- calculus -
**maura**, Friday, September 14, 2012 at 3:34pm
i got a slope of 1/16 is that right?

- calculus -
**Steve**, Friday, September 14, 2012 at 4:05pm
since I have no idea what f(x) is, I can't say. It never appears in the exercise posted.

- calculus -
**Steve**, Friday, September 14, 2012 at 4:06pm
maybe if you showed your calculation of the slope I can figure out how you got it, and whether it's right.

- calculus -
**maura**, Friday, September 14, 2012 at 7:09pm
well the question is from what im assuming is trying to find what f(x) is equal to. thats the last line of my question above. it also wants me to find what a is equal to. so to find slope i took the first derivative: y'= 1/ [2sqrt(x)] since x=64

makes this y'=1/(2*8) = 1/16

- calculus -
**maura**, Friday, September 14, 2012 at 7:11pm
this sentence doesnt look quite right it should look more like this

In this situation, the function is

f(x) = ? a= ?

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