The distance between the points $A$ and $B$ is $\sqrt{5}.$ If $A = (a,-1)$ and $B = (2,2a-7),$ then find the sum of all possible values of $a.$
Using the square of the distance formula
(a-2)^2 + (2a - 7 - -1)^2 = 5
(a -2)^2 + (2a -6)^2 = 5
a^2 -4a + 4 + 4a^2 -24a + 36 = 5
5a^2 - 28a + 35 = 0
Sum of possile a's = 28 / 5
+1678 
