F(x) = x² + 6x - 18 tentukan x jika f-¹ (x) = 2

F(x) = x² + 6x - 18
y = x² + 6x - 18
x² + 6x = y + 18
(x² + 6x + 9) = y + 18 + 9
(x + 3)² = y + 27
x + 3 = + √y + 27
x = -3 + √y + 27
f-¹(x) = -3 + √x + 27

tentukan x

jika f-¹ (x) = 2

f-¹(x) = -3 + √x + 27
2 = -3 + √x + 27
2 + 3 = √x + 27
5 = √x + 27
5² = x + 27
25 = x + 27
x = 25 - 27
x = -2