Diketahui f(x) = 3x + 1 & g(x) = 2x/3x+6 jika (fog)(a) = 7. Tentukan nilai a!

(f₀g)(x) = f(gx)
           = f ( 2x/3x +6)
           = 3( 2x/3x +6)+1
           = 6x/9x + 18 + 1
           = 2x/3x + 19

(f₀g)(a) = 2a/3a + 19 =7
           = 2a/3a = 7-19
           = 2a/3a = - 12

2a/3a = -12
2/3 a  = -12
     a   = -12 x 3/2
          = -36/2
          = -18