Pembahasan:
Fungsi kuadrat f(x) = x² + 3x – 4 memotong sumbu X, maka nilai y = f(x) = 0
x² + 3x – 4 = 0
x² – x + 4x – 4 = 0
(x² – x) + (4x – 4) = 0
x(x – 1) + 4(x – 1) = 0
(x – 1)(x + 4) = 0
x – 1 = 0 atau x + 4 = 0
x = 1 x = -4
Kaprikornus, koordinat titik potong terhadap sumbu X ialah (1,0) dan (-4, 0).