Question

Di ketahui Sn = n² + 2n
Di tanya b(beda) = ... ?

Answer 1

S1 = + 2.1
= 1+ 2
= 3 = U1

S2 = + 2.2
= 4 +4
= 8

S2- S1 = U2
8- 3 = 5

b = U2-U1
=5-3
= 2