+422 The distance between the points (a,21) and (4,7) is 10*sqrt(2) Find the sum of all possible values of a
+36915 Distance formula
sqrt ( (a-4)^2 + (21-7)^2 ) = 10 sqrt 2
sqrt ( (a^2-8a+16) + 196 ) = 10 sqrt 2
a^2-8a+16 +196 = 200
a^2-8a + 12 =0 either factor (in your head ) or use quadratic formula to find the TWO values of 'a'
