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.
a9 = a10 - d, а так как a10 = d, то a9 = d - d = 0
графически или уравнением?
3,6,9,12,15,18,21,24,27,30,33,36,39,42,45,48,51,54,57,60,63,66,69,72,75,78,81,84,87,90,93,96,99