Why is (1 + sqrt(-5) x (1 – sqrt(-5)) equal to 6?
Did you expand the expression?
Do you know about imaginary numbers? You don't have to to calculate the expression, but it helps understanding what is going on.
I don't know how to work with imaginary numbers.
Then just imagine that sqrt(-5) is some number that you don't know. You don't have to use imaginary numbers to solve the problem.
Typo in my original question - a right bracket is missing. It should be,
Why is (1 + sqrt(-5)) x (1 – sqrt(-5)) equal to 6?
You just have a difference of squares: (a+b)(a-b) = a^2-b^2 which, in your case means: (1 + sqrt(-5)) (1 – sqrt(-5)) = 1 - (-5)
Since Juan has shown the OP how to do this, and the OP keeps refusing to show any effort, this thread is now closed (after some cleanup)
Separate names with a comma.