А) =-2,7*0,4=-1,08
б) = 1977/10*10/1=1977
в) = 88/1*10/1=880
B1 = 15
S = 75
q - ?
S = b1/ (1 - q) = 75
15 / (1 - q) = 75
75 (1 - q) = 15
1 - q = 0,2
- q = - 0,8
q = 0,8
√3sinx/3+3cosx/3=0/cosx/3≠0
√3tgx/3+3=0
tgx/3=-√3
x/3=-π/3+πn
x=-π+3πn
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x - любое число