3. Jika f(x) = x2-4x-3, maka f-1(x) = 4. Jika f(x) = 2x2+3x-1, maka f-1(x) = ini yang pake rumus abc x1,2= −b± √b2−4ac/2a

y = x^2 -4x -3
x^2 -4x = y + 3
(x -2)^2 -4 = y +3
(x -2)^2 = y +3 +7
(x -2)^2 = y + 10
(x -2) = +/- V(y+10)
x = 2 +/ - V(y +10)
f-1(x) = 2 +/- V(x +10). ( V adalah ajar)
4) f (x) = 2x^2 + 3x -1
y = 2x^2 + 3x -1
2x^2 + 3x ,= y +1. (kalikan 1/2)
x^2 +3/2x = y/2 + 1/2
(x + 3/4)^2 - 9/16 = y/2 + 1/2
(x + 3/4)^2 = y/2 + 1/2 + 9/16
(x + 3/4)^2 = y/2 + 17/16
x + 3/4 = +/-V(y/2+17/16)
x = -3/4 +/- V(y/2 +17/16)
f-1(x) = -3/4 +/- V(x/2 + 17/16)