Posted by **Pam** on Friday, April 25, 2008 at 7:59am.

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 -
**Reiny**, Friday, April 25, 2008 at 8:21am
I cannot make sense out of your equation, check your typing.

- calculus -
**Reiny**, Friday, April 25, 2008 at 12:33pm
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

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