Find critical numbers of f(x) = 7x^3 + |x|.

I know that you need to find the derivative and set it to equal 0 to find the critical numbers. However, I am being thrown off with the absolute value. Thanks!

Question

Find critical numbers of f(x) = 7x^3 + |x|.

I know that you need to find the derivative and set it to equal 0 to find the critical numbers. However, I am being thrown off with the absolute value. Thanks!

superdavesuper · Answer

there are a few ways to do it...probably the easiest is just separate it into two different eqns:

for x>=1,  f(x) = 7x^3 + x
for x<1,  f(x) = 7x^3 - x

then differentiate as usual n solve for critical point for both. good luck! :)

anonymous · Answer

Oh wow I did not think of that. Thanks!

superdavesuper · Answer

welcome n thanks 4 the medal @brando86