3х+2у=35
х+3у=35 (умножаем на -3)
3х+2у=35
-3х-9у=-105
1) -7у=-70
у=10
2) 3х+20=35
3х=15
х=5
Овтет: (5;10)
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cos x/3<√2/2 π/4+2πn<x/3<7π/4+2πn n∈z
3π/4+6πn<x<21π/4+6πn. n∈z
ответ x∈(3π/4+6πn. 21π/4+6πn) n∈z