Saturday, April 21, 2012

show that √(1 + √(-3)) + √(1 - √(-3)) = √(6)

Let y = √(1 + √(-3)) + √(1 - √(-3))

so y^2 = (√(1 + √(-3)) + √(1 - √(-3)))^2
= (1 + √(-3)) + (1 - √(-3)) + 2 √((1 + √(-3))(1 - √(-3)))
= (1 + √(-3)) + (1 - √(-3)) + 2 √(1 - (-3)))
= 6

so y = √(6) as LHS is positive

hence √(1 + √(-3)) + √(1 - √(-3)) = √(6)

2 comments:

Anonymous said...

How do you get from
This (√(1 + √(-3)) + √(1 - √(-3)))^2

to this? (1 + √(-3)) + (1 - √(-3)) + 2 √((1 + √(-3))(1 - √(-3)))

How do you come to that step? Can you show me each little part squaring the top term?

kaliprasad said...

using (a+b)^2= a ^2 + b^2 + 2ab
and a= √(1 + √(-3)
b = √(1 - √(-3)))

you get a^2 = 1 + √(-3)
b^2 = 1 - √(-3)
2ab = 2 √((1 + √(-3))(1 - √(-3)))
is it not obvious