Jika a dan b adalah nilai maksimum dan minimum dari f(x) = 10 + 4sin4x cos4(x - 1/24[tex] \pi [/tex]), maka nilai a - b adalah... thankyou :)

[tex]f(x) = 10 + 4sin(4x)cos4(x - \frac{1}{24} \pi) \\ f(x) = 10 + 4sin(4x)cos(4x - \frac{1}{6} \pi) \\
f(x) = 10 + 2sin(8x - \frac{1}{6} \pi) + 2sin( \frac{1}{6} \pi) \\ f(x) = 10 + 2sin(8x - \frac{1}{6} \pi) + 2sin( 30) \\f(x) = 10 + 2sin(8x - \frac{1}{6} \pi) + 2( \frac{1}{2}) \\f(x) = 10 + 2sin(8x - \frac{1}{6} \pi) + 2sin( 30) \\ f(x) = 11 + 2sin(8x - \frac{1}{6} \pi) \\
f'(x) = 16cos(8x - \frac{1}{6} \pi) = 0 \\
0 = cos(8x - \frac{1}{6} \pi) \\
cos (90) =cos(8x - \frac{1}{6} \pi) \\ 90 = 8x - 30 \\ 120 = 8x \\ x = 15 \\ \\ atau \\ \\ cos (270) =cos(8x - \frac{1}{6} \pi) \\ 270 = 8x - 30 \\ 300 = 8x \\ x = 37.5 \\ \\ f''(x) = - 128sin(8x - \frac{1}{6}\pi) \\ f''(15) = - 128sin(90) = - 128(1) = - 128 \\ angka \: negatif \: berarti \: nilai \: maksimum \\ \\ f''(37.5) = - 128sin(270) = - 128 (- 1 )= 128 \\ angka \: negatif \: berarti \: nilai \: minimum \\ \\ a - b = 15 - 37.5 = - 22.5 \: atau \: 337.5[/tex]