A = {- 1, 1, 2, 3} এবং B = {x : x2- 2x - 3 = 0} হলে A ∩ B = কত?

প্রশ্ন: A = {- 1, 1, 2, 3} এবং B = {x : x² - 2x - 3 = 0} হলে A ∩ B = কত?

সমাধান: 
B = {x : x² - 2x - 3 =0}
এখন,
x² - 2x - 3 = 0
⇒ x² - 3x + x - 3 = 0
⇒ x(x - 3) + 1(x - 3) = 0
⇒ (x - 3)(x + 1) = 0
হয়, x - 3 = 0 অথবা, x + 1 = 0
∴ x = 3  অথবা x = - 1
∴ B = {- 1, 3} 

এখন,
A ∩ B = {- 1, 1, 2, 3} ∩ {- 1, 3} 
= { - 1, 3}