Answer ;
Sn= 10/2 [2 (5)+(10-1)4]
*10/2 you need to divide it. So the answer was 5.
Sn= 5 [10+(9)4]
*2x5 is equal to 10.
*10-1 is equal to 9.
Sn= 5 [10+36]
*Since when it comes to math you need to follow the PEMDAS means Parenthesis, Exponent, Multiplication, Division, Addition, and Subtract.
Sn= 5 (46)
* multiply it.
Sn=230.
--------------------
ctto
