Respuesta :

18. part 1) x equals 4d square root 5 over 5 . it's a fraction
      part 2) x equals 4 square root 5 over d.  it's a fraction
      part 3) x equals d square root 5 over 4.  it's a fraction
      part 4) x equals 4d square root 5 over 5 (same as part 1)