saya kurang faham menggunakan rumus fungsi invers

f(x) = (2x + 3) / (5x - 1)
y = (2x + 3) / (5x - 1)
y(5x - 1) = 2x + 3
5xy - y = 2x + 3
5xy - 2x = 3 + y
x (5y - 2) = y + 3
x = (y + 3) / (5y - 2)
f-¹(x) = (x + 3) / (5x - 2)
x ≠ 2/5