# Math Help - tangents and limitss

1. ## tangents and limitss

let $f(x)= (x^3+7x^2+9)/(3x)$. Find all of the points on the curve y=f(x) at which the tangent line is horizontal.

I know i'm suppose to find the limit so i can get the slope to the equation of the tangent?

2. Originally Posted by redpanda11
let $f(x)= (x^3+7x^2+9)/(3x)$. Find all of the points on the curve y=f(x) at which the tangent line is horizontal.

I know i'm suppose to find the limit so i can get the slope to the equation of the tangent?
you should find the derivative (do you have to use the limit definition to do that? do you know the power rule?)

when you find the derivative, set it equal to zero. the x's that make the derivative zero are the x-values you want

3. i have to use the definition so no power rule. But thank you, i know where to go from here i was just unsure

4. Originally Posted by redpanda11
i have to use the definition so no power rule. But thank you, i know where to go from here i was just unsure
ok. post your solution when done...just to be sure