Equation of the tangent line to the curve

  • Thread starter kdpointer
  • Start date
  • #1
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Homework Statement



Find an equation of the tangent line to the curve: 7*x*e^(x)+8 at (0,8)

Homework Equations



Derivative I guess?

The Attempt at a Solution



I know you have to take the derivative of the equation given which I think is

7*x*e^(x) + 7*e^(x)

Then you plug it into slope intercept form: y-y=m(x-x)

I did this and got y-8=(7*e^(x)*(x+1))*x, but apparently that's not right...

What did I do wrong? Maybe i just typed it in wrong?
 

Answers and Replies

  • #2
learningphysics
Homework Helper
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Calculate the slope first by plugging in x=0 into the derivative equation... then when you have the number for the slope, plug it into the slope intercept form.

The slope should just be a number.
 
  • #3
Dick
Science Advisor
Homework Helper
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Yeah, it's pretty wrong. In the line equation m is a constant. Otherwise, it wouldn't be a line, now would it? Put (0,8) into the derivative before you plug it into the line equation.
 
  • #4
1,753
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so essentially you have to use your x-intercept twice
 
  • #5
14
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So the slope is just 7?
 
  • #6
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Thus the final equation is y-8 = 7x ?
 
  • #7
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Thus the final equation is y-8 = 7x ?
it should probably be in slope-intercept form

y=mx+b
 
  • #8
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It says that point-slope form is fine.. but it would be y=7x+8
 
  • #9
learningphysics
Homework Helper
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It says that point-slope form is fine.. but it would be y=7x+8

Yup. That's right.
 
  • #10
14
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Alright.. thanks a lot!
 

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