# critical point of graph

• March 12th 2011, 10:58 AM
jackopp
critical point of graph
i want to find the critical point of the graph
$x^4+x^3-18x^2+24x$

i done that, but have difficulties then
f'(x)=4x^3+3x^2-36x+24
then f'(x)= 0 is critical point, but i don't know how to solve f'(x)=0.........
• March 12th 2011, 12:03 PM
skeeter
Quote:

Originally Posted by jackopp
i want to find the critical point of the graph
$x^4+x^3-18x^2+24x$

i done that, but have difficulties then
f'(x)=4x^3+3x^2-36x+24
then f'(x)= 0 is critical point, but i don't know how to solve f'(x)=0.........

f'(x) = 0 has no rational roots ... you'll need to use technology to approximate them.