Если f(x)=1x,то f(x+3)=1x+3/ 10f(x+8)=10(1x+8)=10x+80
x+3=10x+80
-9x=77
x=-77\9= -8 5\9
делаем проверку
-77\9+3=10(-77)\9+8
-77+27\9=10(-77+72)\9
-50\9=-10*5\9/ -50\9=-50\9 доказано
6) D
7) A
8) 6.5
9) 4
10) 1-c, b
2- e, a
3-d
См. вложение
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1.4 sin(7π/6)+ctg(5π/4) = 4 sin(π + π/6)+ctg(π + π/4) = 4 sin(π + π/6)+ctg(π + π/4) = -4sin(π/6) + ctg(π/4) = -2 + 1 = -1
2. 2cos^2a-cos2a=2cos^2a - cos^2a + sin^2a = cos^2a+sin^2a=1
3.sin2a=2sina*cosa
cosa=-1/√5
sina=√(1-( -1/√5)^2) = √(1-1/5)= √(4/5) = 2/√5
Sin2a = 2 * 2/√5 *(-1)/√5 = -4/5 = -0,8