Carilah x bila f(x)=–1/3x³–5/2x²+6x+7 turun

kurva f(x) turun jika f'(x)<0
f'(x)<0
-x^2-5x+6<0
x^2+5x-6>0
(x+6)(x-5)>0
x=-6 x=5

+ - +
------------------------
-6 5

karena tanda besar maka yg diambil (+)
HP={x|x<6 atau x>5, x e real}

f(x) = -1/3 x^3 - 5/2 x^2 + 6x + 7 turun jika f'(x) < 0
f'(x) = -x^2 - 5x + 6 < 0
=> - (x^2 + 5x - 6) < 0
=> - (x + 6)(x - 1) < 0
=> x = -6 atau x = 1
---- (-6) +++ (1) +++
x < -6 atau x > 1