Question

Find the coordinates of the inflection points and critical points of f (x) = 4x5 – 100x3 – 5.

Answer 1

y=4x^5 -100x^3-5

dy/dx=20x^4-100x^2

d2y/dx=80x^3-100.....slope chaenj from + tu minus at x^3=100/80

x^3=1.25, so x=1.077217345015942

Answer 2

woops...y=4x^5 -100x^3-5

dy/dx=20x^4 -300x^2

d2y/dx=80x^3 -600x

inflex point...set this =0, so x=0

or 80x^2-600=0, x^2=600/80=7.5

x=sqrt(7.5)=+-2.738612788