jika fungsi g(x) = 2x - 4 dan (gof) (x) = 4x² - 20x + 26, nilai f(-1) adalah..

(gof)(x) = 4x² - 20x + 26
g(f(x) = 4x² - 20x + 26
2(f(x) - 4 = 4x² - 20x + 26
2(f(x) = 4x² - 20x + 26 + 4
2(f(x) = 4x² - 20x + 30
f(x) = (4x² - 20x + 30)/2
f(x) = 2x² - 10x + 15

f(-1) = 2(-1)² - 10(-1) + 15
f(-1) = 2(1) + 10 + 15
f(-1) = 2 + 10 + 15
f(-1) = 27