gradien garis singgung kurva y=

f(x) = 2x^3 - 9x^2 + 12x naik jika f'(x) > 0
f'(x) = 6x^2 - 18x + 12 > 0
=> x^2 - 3x + 2 > 0
=> (x - 2)(x - 1) > 0
=> x = 2 atau x = 1
Garis bilangan
+++ (1) --- (2) ++++
Interval naik : x < 1 atau x > 2