Let a and b be real numbers such that a + b = -1. Compute a^2 - b^2 + 3a + b.
Note the entire expression is 2(a + b), so substitution gives a^2 - b^2 + 3a + b = -2.
a^2 - b^2 + 3a + b
(a + b) (a - b) + 3a + b
(-1)(a - b) + 3a + b =
-a + b + 3a + b =
2a + 2b =
2 ( a + b) =
2 (-1) =
-2.......just as HSD found !!!!!!
GREAT SOLUTION
+137 
