1. (3ⁿ+3ⁿ⁻¹)²=(3ⁿ+3ⁿ/3)²=(3ⁿ+(3ⁿ/3))²=((3*3ⁿ+3ⁿ)/3)²=(4*3ⁿ/3)²=(4*3ⁿ⁻¹)²=16*3²ⁿ⁻².
2. 9ⁿ⁻¹=3²*⁽ⁿ⁻¹⁾=3²ⁿ⁻².
3. 16*3²ⁿ⁻²/3²ⁿ⁻²=16.
A1 = 2,
a6 = 17
d = 3;
a10= a1 + 9d = 2 + 9*3 = 2 + 27 = 29
S10= (a1 + a10)/2 * 10 = 5* (2 + 29)= 155
!!!!!!!!!!!!!!!!!!!!!!!!!!!!
.......................................................