For the curve y = (1/3)x^3, given that 24x + 3y +2 = 0 is the equation of the tangent to the curve at the point (p,q) find p and q.(adsbygoogle = window.adsbygoogle || []).push({});

I rearranged to get y = -8x - 2/3

So the tangent gradient is -8

I differentiated to get x^2 - 9

Therefore x^2 - 9 = -8 and x = 1 or x = -1.

From here how do I distinguish whether x = 1 or x = -1?

Many thanks.

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Geometry problem

**Physics Forums | Science Articles, Homework Help, Discussion**