for what values of a and b is the line 2x+y=b tangent to the curve at y=ax^2 at x=-4

help would be welcome, thanks in advnace (Nod)

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- Oct 15th 2008, 09:53 PMsxustevencalculus/derivative question
for what values of a and b is the line 2x+y=b tangent to the curve at y=ax^2 at x=-4

help would be welcome, thanks in advnace (Nod)

- Oct 15th 2008, 09:56 PMmr fantastic
- Oct 15th 2008, 09:59 PMChris L T521
Rewrite the equation of the line as

The slope of this line is

Now, differentiate the function to get

At x=-4, the value of the derivative is .

Now when is ?

Once you have a, then plug the point into the function to find the value of the function at this point [which I will call ].

Then, take this point and plug it into the equation for the line:

, where is the point on the function (and on the line)

Then solve for b.

Can you take it from here?

--Chris