cara dan penyesesaian

jawab

f(x) = ax² +8x -12
f'(x) = 2ax +8
f' (4) = 28
2a(5) + 8 = 28
10a + 8 = 28
10a = 20
a = 2

3a² - 2a = 3.2² - 2(2) = 12 - 4 = 8