17х+7х=10у+2
24х=10у+2
24х=12у
ху=24:12
ху=2
(2;2)
1)925-825=100, 527+100=627
2) 2/19*19=2 ,2*13,5=27,27/4=6.75
3)2/17*17/21=2/21 , 3/11 * 4/3=4/11 , 2/21*4/11 = 8/231
Решение
a₆ = 5 a₅ = 21
a₆ = a₅ + d
d = a₆ - a₅ = 5 - 21 = - 16
a₅ = a₁ - 16*4
a₁ = a₅ + 64 = 21 + 64 = 85
a₁₀ = a₁ + 9d = 85 - 9*16 = - 59
Sn = (a₁ + a₁₀)*10 / 2 = (85 - 59)*5 = 130