9-10 pakai jalan ya bsk dikumpul

9. a = 1
    b = 3
    Un = a + (n-1)b
          = 1 + (n-1)3
          = 1 + 3n - 3
          = 3n - 2
  Jawaban B

10. a = 3
      b = 1
      c = 2
    
     Un = [tex] \frac{a}{0!} + \frac{(n-1)b}{1!}+ \frac{(n-1)(n-2)c}{2!} [/tex]
           = [tex] \frac{3}{1} + \frac{(n-1)1}{1} + \frac{( n^{2} -3n+2)2}{2} [/tex]
           = 3 + n-1 + n² - 3n + 2
           = n² - 3n + n - 1 + 2 + 3
           = n² - 2n + 4

Jawaban C