f = (x^3-8) / (2*x^2-8)
umformen
f = (x^3-8) * (2*x^2-8)(^-1)
u = x^3 - 8
u ´ = 3*x^2
v = (2*x^2-8)(^-1)
v´ = (-1)(2*x^2-8)(^-2) * 4x
v´ = (-4x*)(2*x^2-8)(^-2)
( u * v ) ´ u´ * v + u * v´
3*x^2 * (2*x^2-8)(^-1) + ( x^3 - 8 ) * (-4x*) * (2*x^2-8)^(-2)
3*x^2 / (2*x^2-8 )^(-1) + ( -4*x^4 + 32*x ) / (2*x^2-8)^(-2)
3*x^2 * (2*x^2-8 ) / (2*x^2-8 )^(-2) + ( -4*x^4 + 32*x ) / (2*x^2-8)^(-2)
( 6*x^4 - 24x^2 -4*x^4 + 32*x ) / (2*x^2-8)^(-2)
( 2*x^4 - 24x^2 + 32*x ) / (2*x^2-8)^(-2)
Extremwert : Zähler = 0
2*x^4 - 24x^2 + 32*x = 0
Satz vom Nullprodukt anwenden
x * ( 2*x^3 - 24x + 32 ) = 0
x = 0
und
2*x^3 - 24x + 32 = 0
x^3 - 12x + 16 = 0
Raten oder Probieren
x = -4
(-4)^3 - 12 *(-4) + 16 = 0
-64 + 48 + 16 = 0 stimmt
x = 0
und
x = -4