⇒ (x+1)(x+2) – (x–1)(x–3) = 4 × 3 – 1 × (–1)

⇒ (x² + 2x + x + 2) – (x² – 3x – x + 3) = 12 + 1

⇒ –2x –1= 13

⇒ –2x = 14

⇒ x = –7