ax² - 13x +b = 0; x=2/3 and 3/2 then find a and b

a x²-13 x + b =0
p(2/3) = a(2/3)²- 13 (2/3) + b =0 
          = 4 a/9 - 26/3 +b =0 
           ( taking LCM as 9 )
          = 4 a - 78 +9 b =0 ----- 1
p ( 3/2) = a [ 3/2]² - 13 [ 3/2 ] +b =0
          after solving the equation ----- 9 a - 78 +4 b = 0 ------- 2 
adding 1 and 2 
    13 a +13 b= 156 -------3
subtracting 1 and 2 
     -5 a+5 b=0
       a=b -------4
putting 4 in 3 
    13 a + 13 b = 156
   13 a + 13 a = 156
   26 a = 156
  a = 6
  therefore : b=6