Question

Jika m dan n bilangan real dan fungsi f (x) = mx³ + 2x² - nx + 5 memenuhi f ' (1) = f ' (-5) = 0, maka 3m - n = ....

Answer 1

Kita turunin dulu
F'(x) = 3mx^2 + 4x - n
F'(1)= 3m+4-n = 0
3m-n=-4
F'(-5)=3m.25 + 4.-5 - n
75m -20 - n = 0
75m - n = 20

75m-n=20
3m-n=-4
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72m = 24
M = 24/72 = 1/3
3m-n=4
3.1/3-n=4
1-n=4
N = -3

3m-n = 3.1/3 -(-3) = 1+3 = 4