a = 3 + sqrt ( 5a - 9)
a - 3 = sqrt (5a - 9) square both sides
(a - 3)^2 = 5a - 9
a^2 - 6a + 9 = 5a - 9 subtract 5a, add 9 to both sides
a^2 - 11a + 18 = 0 factor
(a - 9) ( a - 2) = 0
Setting both factors to 0 and solving for a gives that
a = 9 or a = 2
Check 9 Check 2
9 = 3 + sqrt ( 5*9 - 9) 2 = 3 + sqrt ( 5*2 - 9)
9 = 3 + sqrt (36) 2 = 3 + sqrt !
9 = 3 + 6 2 = 3 + 1
good 2 = 4
no good
So....the only answer is a = 9