1. Jika f(x) = ax + bx² dan f¹(1) = 5 dan f¹(2) = 7, maka nilai ab = ... 2. Diketahui y = (3x - 4)². Supaya dy/dx = 12, maka nilai x = ...

1. f(x) = ax + bx²
f'(x) = a + 2bx

5 = a + 2b
7 = a + 4b
--------------- -
-2 = -2b
b = 1

5 = a + 2
a = 3

ab = 3 × 1 = 3

2. y = (3x - 4)²
y' = 2(3x - 4) × 3 = 6(3x - 4)
18x - 24 = 12
18x = 36
x = 2