4x^3+36x=0=4x(x^2+9)
solutions are at 3i, and Zero.
now look at x=0
find the intervals on which f(x) is increasing and decreasing along with the local extrema.
f(x)=x^4 + 18x^2
I took the derivative and got:
f'(x)= 4x^3 + 36x
When I set this to zero, I get the imaginary number 3i. I can't get test values for an imaginary numbers, so I can't find the extrema. Does this have no solution?
2 answers
bobpursley can u check my work?
1 answer