Question

1+3+5+......+(2n+1)=144

Answer 1

SSH:[(2n-1)]:1+1=n+1

Tổng: (2n+1+1)* (n+1):2=144<=>2(n+1)(n+1):2=144<=>(n+1)(n+1)=144

=>n+1=12

=>n=11

Answer 2

Số các số hạng:

(2n + 1 - 1):2 + 1 = n + 1 (số)

(n + 1).(2n + 1 + 1) : 2 = 144

(n + 1).2(n + 1):2 = 144

( n + 1)² = 144 = 12²

n + 1 = 12 => n = 11