Thread: Solving for x in derivative = 0

Thank you in advance for your help.

I have found the derivative of f(x) from a previous problem, and now I must set the derivative to 0 since I am now finding the function of x values where the tangent is horizontal, meaning that the slope is 0.

Here is where I am in the problem:

3x^2-8x-7=0

in an attempt to move x to one side and numbers to the other:

x^2-8x=7(1/3)

since x^2=2x

2x-8x=7(1/3)

But how do I get rid of the two x's since there is only supposed to be one x on the left side?

Sorry, I'm stuck!

Originally Posted by theredqueentheory

Thank you in advance for your help.

I have found the derivative of f(x) from a previous problem, and now I must set the derivative to 0 since I am now finding the function of x values where the tangent is horizontal, meaning that the slope is 0.

Here is where I am in the problem:

3x^2-8x-7=0

in an attempt to move x to one side and numbers to the other:

x^2-8x=7(1/3)

since x^2=2x

2x-8x=7(1/3)

But how do I get rid of the two x's since there is only supposed to be one x on the left side?

Sorry, I'm stuck!

Use the quadratic formula:

If, (which is unusual) then is equal to