(√23 - 1)(√23 + 1)(√22 - 1)(√22 + 1) =

Question

(\sqrt{23}-1)(\sqrt{23}+1)(\sqrt{22}-1)(\sqrt{22}+1)=

A. 154
B. 231
C. 462
D. 529
E. 625

chetan2u · Answer

It uses the formula  (a-b)(a+b)=a^2-b^2

(\sqrt{23}-1)(\sqrt{23}+1)(\sqrt{22}-1)(\sqrt{22}+1)= 
 (\sqrt{23}^2-1^2)(\sqrt{22}^2-1)=(23-1)(22-1)=22*21=462

C

Fdambro294 · Answer

Difference of squares:

*   =

(23 - 1) * (22 - 1) =

(22) * (21) =
462

C

Posted from my mobile device

Abhishek009 · Answer

(\sqrt{23}-1)(\sqrt{23}+1)(\sqrt{22}-1)(\sqrt{22}+1)

Or,  (23 - 1)(22 - 1)

Or,  22*21

Units digit must be 2 (As 1*2 = 2) , among the given options only (C) fits in perfectly, hence Answer must be (C)

Prep Toolkit