Question

how to factorize -(a^2 +b^2)?
does it equal to -(a^2+2ab+b^2)?

Answer 1

Ever heard of the "difference of two squares" rule? It states that:
\[\Large {a^2} - {b^2} = (a + b)(a - b)\]
In your case:
\[\Large \begin{array}{l}
- ({a^2} + {b^2})\\
= {b^2} - {a^2}\\
= ...
\end{array}\]

Answer 2

thx=]

Answer 3

No worries =) A medal would be nice though :-P