If x4 + 2x3 + ax2 + bx + 9 is a perfect square, where a and b are positive real numbers, then the value of a and b are

• ক a = 7, b = 8
• খ a = 7, b = 6 ✅ সঠিক উত্তর
• গ a = 5, b = 6
• ঘ a = 6, b = 7