Let a and b be real numbers such that a + b = -1. Compute a^2 - b^2 + 2a.
The answer can be written out as an expression in terms of $a$ alone or $b$ alone. You need to know either the value of $a$ or $b$ in order to know the exact value of $a^2-b^2+2a$.
\(a^2-b^2+2a\)
\(=(a+b)(a-b)+2a\)
\(=-1(a-b)+2a\)
\(=-a-(-b)+2a\)
\(=b-a+2a\)
\(=b+a\)
\(=-1\)
You're right. I made an incorrect observation.
