SOLUTION: Find the equation of the tangent to the graph at the indicated point. f(x) = x^2 − 7x; a = −8

Algebra ->  Test  -> Lessons -> SOLUTION: Find the equation of the tangent to the graph at the indicated point. f(x) = x^2 − 7x; a = −8      Log On


   



Question 1118669: Find the equation of the tangent to the graph at the indicated point.
f(x) = x^2 − 7x; a = −8

Found 2 solutions by Alan3354, greenestamps:
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
How is "a" related to the equation?
a = -8 is not a point.
==========
IMO, it's not clear what the problem is.
Math is known for being an exact science.
It's important to know what you want to do, and to say exactly what you want to do.
------
In this problem, no relation is given between the equation and a.
Or b, or c, or z, etc.
----
I did think it was likely you meant at the point where x=a, but it's not my job to figure out what you might mean. You need to state what you want to do clearly and unambiguously.
---------
PS I don't get paid extra for submitting more responses/solutions.
PPS I have never "bad-mouthed" another tutor. We all do this for altruistic reasons. And, I think learning how to post a problem clearly is a lot more important than getting the answer to this problem.

Answer by greenestamps(13195) About Me  (Show Source):
You can put this solution on YOUR website!


It's quite clear what your question is. Unfortunately, there are a few "tutors" here who like to increase the number of questions they have "answered" by being nitpickers about how you present the problem.

f(x) = x^2-7x; f(a) = f(-8) = 64+56 = 120

f'(x) = 2x-7; f'(a) = f'(-8) = -16-7 = -23

The point of tangency is (-8,120); the slope at that point is -23. The equation is

y-120+=+-23%28x-%28-8%29%29
y-120+=+-23%28x%2B8%29
y+=+-23%28x%2B8%29%2B120

There are of course many different forms in which this equation can be shown.