1/4m^6n^9*(-8/27m^3n^6)= -2/27m^9n^15.
Это номер 2 (а, б, в г), номер 3 и номер 4
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2cos^2x-1-sin4x=0
cos2x-2sin2xcos2x=0
cos2x=0
x=П/4+Пn/2
1-2sin2x=0
sin2x=1/2
x=П/12+Пk
x=5П/12+Пk
(a^2 - 36) / (2a^2 + 12a) = (a - 6)(a +6)/(2a / (a + 6) = (a -6 ) / 2a
a = - 0.3
(-0.3-6)/(2*(-0.3) = -6.3 / -0.6 = 10.5