materi fungsi inves,mohon bantuan

1. f(x) = { (2,1), (3,2), (2,3) } ---> koordinatnya tukar tmpt aj.
2. 
f(x) = 2x + 5
{ganti f(x) -> y, terus buat x jd subjek}
y = 2x +5
x = (y-5)/2
{ganti x-->f⁻¹(x) dan y-->x}
f⁻¹(x) = (x-5)/2
f⁻¹(2) = (2-5)/2 = -1.5