f(x) = -6/5 x^4 + 27/5 x^2 - 12/5
f ' (x) = -24/5 x^3 + 54/5 x
f '' ( x) = -72/5 x^2 + 54/5
bis hierhin richtig?
f ' (x) = -24/5 x^{3} + 54/5 x = 0
-24 x^{3} + 54 x = 0
6x(-4x^2 + 9) = 0
6x(3-2x)(3+2x)=0
x1 = 0
x2 = 3/2
x3 = -3/2
f '' ( x) = -72/5 x^2 + 54/5
f '' ( 0) = 54/5 > 0 ==> P(0 | -12/5) ist relatives Minimum
f ''(3/2) = -72/5 1.5^2 + 54/5 < 0 ==> Q(1.5 | f(1.5)) relatives Maximum
f ''(-3/2) = -72/5 (-1.5)^2 + 54/5 < 0 ==> R(1.5 | f(-1.5)) relatives Maximum
Kontrolle
~plot~ -6/5 x^4 + 27/5 x^2 - 12/5 ~plot~