(a + b + c − d)2 − (a − b − c + d)2 = ?
Answer & explanation
Correct answer: option 2
We know that,
a2 - b2 = (a + b) (a – b)
a = (a + b + c − d)
b = (a − b − c + d)
(a + b + c − d)2 − (a − b − c + d)2
= (a + b + c − d + a − b − c + d) (a + b + c − d – a + b + c - d)
= (2a) (2b + 2c - 2d)
= 4a(b + c − d)