Question

1 plus 3 plus 5 plus puncte puncte plus 2 n minus 1 paranteză​

Answer 1

1 + 3 + .. + 2n - 1 =

= (2·1 - 1) + (2·2 - 1) + .. + (2·n - 1)

= 2(1 + 2 + .. + n) - n

= 2×n(n + 1) : 2 - n

= n(n + 1) - n

= n(n + 1 - 1)

= n×n

= n²