Jawabanmu

2014-03-10T21:37:16+07:00
Un = a + (n-1)b                 * mencari b = 17- 20 = -3
U50 = 20 + (50 - 1) -3
U50 = 20 + 49. -3
U50 = 20 + (-147)
U50 = -127
2014-03-10T21:39:26+07:00
Un = a+(n-1) b u50= 20+(50-1)-3 = 20+(49.3) 20+(-147) =-127