Question

simplify (-2-root3) (-2 + root3)

Answer 1

Here a=-2 & b=root3 so by using a2-b2=(a+b)(a-b) we have, (-2)whole sq. - (root3)whole sq. 4-3=1

Answer 2

(-2-√3)(-2+√3)
basically this is 
(a+b)(a-b)
=a²-b²
⇒-2²-√3²
⇒4-3
⇒1

Ans=1