(1)f(x))'=(2sinx+0,5)=(2sinx)'+0,5'=
2 cosx
2)f(x)'=(3sinx-1,5cosx)'=(3sinx)'-(1,5cosx)'
=3cosx+1,5sinx
3/7*4=12/7=1 5/7
4/8*100=50
13/5:9=3/9
14/81:10=7/405
Х - 3/8х = 1 1/4
5/8х = 5/4
х = 5/4 : 5/8 = 5/4 * 8/5 = 8/4
х = 2
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Проверка: 2 - 3/8 * 2 = 1 1/4
2 - 3/4 = 1 1/4
1 4/4 - 3/4 = 1 1/4
1 1/4 = 1 1/4