You are here:

Calculus/equation to a tangent line

Advertisement

Expert: Alon Mandes - 5/31/2009


Question
On the graph (x^2-5x+4)/(x^3-2x^2-8x) what is the equation for the tangent line at the point (-1,2)?

I got (-x^4+10x^3-30x^2+16x+32)/(x^3-2x^2-8x)^2 for the first derivative, but I'm not positive if that is right.

I used y-y1=m(x-x1) and got y-2=-1(x+1) but when I graphed it it wasn't right. I'm either doing it wrong, or I messed up the drivative.

help please!

Answer
The derivative is correct . & the slope is -0.92 . The equation of
the tangent line is not correct!!
y-y1=m(x-x1) where m is the slope ("the value of the derivaive you
calculated by substituting x=-1 ").
y-2=-0.92(x+1) -> y-2=-0.92x-0.92 -> y=-0.92x+1.08 This is the tangent line .

Alon.

Calculus

All Answers

Answers by Expert:

Ask Experts

Volunteer

Alon Mandes

Expertise

Kind of questions I can answer : Limits, Derivatives, Integration, Implicit functions, continuousity, differentiation ,Extremum problems, Lagrange multipliers, Gradients, Surface integrals, Multi variables functions ,Multi variables Integrals,Complex variables ,Complex functions, Curves, Trajectory integrals & Vector analyse,Divergence,Rotor & word problems. Kind of question I can't answer : Economics,Combinatorics,infinite series & convergence ,Statistics & Probabilities .

Experience

1. I'm a team member of mathnerds (math site for answering questions) 2. I'm a team member in the Student's Union of the Technion, helping students who have problems in mathematics. 3. 2 years of experience as a math teacher in college. 4. I give free homework help for high school students in Mathematics & Physics. 5. I teach part time in collage the subjects : "Digital Signal Processing" , "Random Signals & Noise" , "Complex Functions".

Organizations
Hi-Tech company : GSM4VOIP ; job possition : Algorythm developer.

Education/Credentials
M.A in Mathematics & Bs.c in Electronics.

©2012 About.com, a part of The New York Times Company. All rights reserved.