Posted by **Jen** on Sunday, November 19, 2006 at 5:11pm.

f(x) = x^4 + ax^2

What is a if f(x) has a local minimum at x=5.

How do I justify the answer.

The first derivative has to be zero at x = 5. You then check what the second derivative is at x = 5. If it is positive then that's ok.

In this case you find that a = -50 and that the second derivative at x = 5 is positive.

## Answer This Question

## Related Questions

- math - Find the value(s) of x for the following. (Enter your answers as a comma-...
- Differentiation - Again, that all makes sense. Thank you very much. Thank you ...
- Calculus - Let g be a function that is defined for all x, x ≠ 2, such that...
- Math - find any stationary points of the function g(x) = (2x-3)square root of 5+...
- calc. - I'm having a lot of trouble with this problem: Sketch the graph and show...
- Calculus- answer check - A brand new stock is also called an initial public ...
- Calculus (pleas help!!!) - Let p(x)=x^2(a−x), where a is constant and a ...
- Math - need to classify to stationary points as local minimum and local maximum ...
- Maths - The slope of a curve Y = f(x) is given by dy/dx=(X-1)(x-2)^2(x-3)^3(x-4...
- Calc - 1. Find values of a,b,c, and d such that g(x) = a(x^3)+b(x^2)+cx+d has a ...

More Related Questions