fungsi invers dari f(x)= -3x pangkat 2 + 2 per x+10

f(x) = -3x^2 + 2x + 10
y = -3x^2 + 2x + 10
kedua ruas dibagi -3
-3y = x^2 - (2/3)x - 10/3
-3y = (x - 1/3)^2 - 1/9 - 10/3
-3y = (x - 1/3)^2 - 31/9
-3y + 31/9 = (x - 1/3)^2
(√(-27y + 31))/ 3 = x - 1/3
((√(-27y + 31))/ 3) + 1/3 = x
(√(-27y + 31)+ 1)/ 3 = x
invers fungsi f(x) = (√(-27x + 31)+ 1)/ 3