a + b = √7 এবং a - b = √5 হলে, 8ab(a2 + b2) = কত?

a + b = √7 এবং a - b = √5 হলে, 8ab(a² + b²) = কত?

A 48

B 36

C 24

D 12

Correct Answer: Option C

8ab(a²+b² )
=4ab.2(a²+b² )
={(a+b)²-(a-b)²}{(a+b)²+(a-b)²}
={(√7)²-(√5)²}{(√7)²+(√5)²}
=(7-5)(7+5)
=2×12
=24