# calculus

posted by .

Please help, my live tutor and I could spent 2 hours trying to solve these two:
find an equation for tangent line y=-1-8^2@ (-4,-129)

find the derivative of the function:----we both kept getting the same answer, but Mathlab kept saying that it was wrong: -4lnl3xl/2+3x
we did the quotient rule, and the chain rule...the derivative and our sign would be wrong...

• calculus -

I cannot make sense out of your equation, check your typing.

• calculus -

-4 ln l3xl
2+3x
-4ln absolute value of 3x over 2+3x

y= -1-8x^2
(-4,-129)
the first set is in fraction form.
the 3x is absolute.
the 8x^2 is 8x squared.

• calculus -

for the derivative using the quotient rule I got (-8 - 12x + 12x(ln(3x))) / (x(2+3x)^2)

for the tangent question
dy/dx = -16x

at the point the slope is -16(-4) = 64

so using y = mx + b for the tangent equation
-129 = 64(-4) + b
b = 127

so the tangent equation is y = 64x + 127

• calculus -

Thanks. One small error? I can see what we did wrong..we did not do the
-129= part.....guess we were tired, or tried to do it in our heads.

## Respond to this Question

 First Name School Subject Your Answer

## Similar Questions

1. ### Calculus - Tangent Line

Hi, im having problems with the following problem. The main issue is actually starting the problem. Find the two points on the curve y = x^4 - 2x^2 - x that have a common tangent line. First, find the derivative of y(x) so that you …
2. ### Math- Calculus

Find an equation of the line that is tangent to the graph of f and parallel to the given line Function: f(x) = x^3 Line 3x-y+1 = 0 ._.; I know the derivative of the function is 3x^2 and I do have the answer in the back of my book just …
3. ### Calculus - Damon

Find the line which passes through the point (0, 1/4) and is tangent to the curve y=x^3 at some point. So I found the derivative which is 3x^2. Let (a, a3) be the point of tangency. 3x^2 = (a3 - 1/4)/(a-0) I'm not sure how to solve …
4. ### cal

find the equation of a quadratic function whose graph is tangent at x=1 to the line whose slope8, tangent at x=-2 to solve the line with slope-4 and tangent to the line y=-8 find the equation of the tangent lines at x=1 and x=-2 graph …
5. ### Derivative Calculus

I just need my answers checked. 1) Find the derivative. f(x)=3x^5/4 - 8/9x^9/8 + x^2 - 9x + 1 Answer: f’(x)= 15/4x^1/4 - x ^1/8 + 2x -9 2) Let f(x)= 7x^3 - 9x. Find f’(5) Answer: f’(x)=21x^2-9 f’(5)=516 3) Find the given limit …
6. ### Calculus

1. a) For the Function and point below , Find f’(a). b) Determine the equation of the line tangent to the graph of f at (a,f(a)) for the given value of f(x) = 4x2+2x, a =1 F’(a) = y = 2. For the function find f’ using the definition …
7. ### Calculus

1. a) For the Function and point below , Find f’(a). b) Determine the equation of the line tangent to the graph of f at (a,f(a)) for the given value of f(x) = 4x2+2x, a =1 F’(a) = y = 2. For the function find f’ using the definition …
8. ### Calculus

If F(x)=x^3−7x+5, use the limit definition of the derivative to find FŒ(5), then find an equation of the tangent line to the curve y=x^3−7x+5 at the point (5, 95). FŒ(5)= The equation of the tangent line is y = x …
9. ### calculus

1. Which of the following expressions is the definition of the derivative of f(x) = cos(x) at the point (2, cos(2))?
10. ### Math (equation of tangent line)

Consider the implicit equation 2xy-1=(x+y+1)^2 a) Compute and solve for the derivative dy/dx as a function of x and y. b) Find the equation of the tangent line to the graph of the above when y=-1. For part a, I found the derivative …

More Similar Questions