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По формуле синус суммы sin74·cos16+cos74·sin16= sin(74=16)=sin90=1
1) 0.2х+1.1х=1.4-2.7
1.3х=-1.3
х=1.3:1.3
х=-1
2) 5.4+3.6=0.3х+1.5х
9=1.8х
х=9:1.8
х=5
3) 1/8х-1/6х=10-15
-1/24х=-5
х=-5:(-1/24)
х=120
[1/a(a+2b) - 1/a(a-2b)]:[4b²/(4b²-a²) =
(2a + 1)² - (a - 9)² = (2a + 1 + a - 9)(2a + 1 - a + 9) = (3a - 8)(a + 10)