Question

найти а (п) и d арифметической прогрессии, у которой а1 = 2 1/3, п = 10, S(10) = 90 5/6

Answer 1

2 1/3=7/3; 90 5/6=545/6;
S10=(a1+a10)*10/2;
545/6=(7/3 + a10)*5;
a10 + 7/3=545/6*5;
a10=109/6 - 7/3;
a10=95/6;
a10=a1+(10-1)*d;
d=(a10-a1)/9;
d=(95/6 - 7/3)/9=81/6*9=1,5;