diketahui f(x) = ×^2-8x+20, tentukan f^-1(x) . Tolong bantuin yaa

f(x) = x² - 8x + 20
y = x² - 8x + 20
x² - 8x = y - 20
(x² - 8x + 16) = y - 20 + 16
(x - 4)² = y - 4
x - 4 = ± √y - 4
x = 4 ± √y - 4
f-¹(x) = 4 ± √x - 4