Sn=4n^2 +7 maka U(n+3) adalah........

Deret

Sn = 4n² + 7

Un = Sn - S(n-1)
Un  = 4n² + 7 - { 4(n-1)² + 7}
Un  = 4n² + 7 - 4(n-1)² - 7
Un = 4n² - 4(n-1)²

U(n+3) = 4(n+3)² - 4 (n+3-1)²
U(n+3) = 4(n+3)² - 4(n+2)²
U(n+3) = 4 {(n+3)² -(n+2)²}
U(n+3) = 4 {(n+3+n+2)(n+3-n-2)}
U(n+3) = 4 (2n+5)(1)
U(n+3)= 4(2n+5)  atau  U(n+3) = 8n+20