Maths question - need help!

vanlam8

Does anyone know how to calculate this? thanks a lot!

cafeva

vanlam8 發表於 20-12-4 01:42
Does anyone know how to calculate this? thanks a lot!

2n+3right?

djf

回覆 cafeva 的帖子

S(n)=n[2a+(n-1)d]/2
6(2a+5d)/2 = 60   ----- (i)
7(2a + 6d)/2 = 77 ----- (ii)


d = 2, a = 5

T(n) = 10 + 2(n-1)
T(n) = 3 + 2n