tolong kerjakan no 30

f(x) = x^3 - 9x^2 + 15x + 10
f'(x) = 3x^2 - 18x + 15 = 0
=> x^2 - 6x + 5 = 0
=> (x - 1)(x - 5) = 0
=> x = 1 atau x = 5
Garis bilangan
+++ (1) --- (5) +++
f(1) = 1^3 - 9(1)^2 + 15(1) + 10 = 1 - 9 + 15 + 10 = 17 => (1,17)
f(5) = 5^3 - 9(5)^2 + 15(5) + 10 = 125 - 225 + 75 + 10 = -15 => (5,-15)

A) titik stasioner
1) (1, 17) => titik balik maksimum
2) (5, -15) => titik balik minimum

B) interval fungsi naik : x < 1 atau x > 5

C) interval fungsi turun : 1 < x < 5