5a-4ab=a(5-4b); 4pm^3+10pm^6=2pm^3(2+5m^3).^ -это степень.
-6(4-х)+(у+5)=2
-24+6х+у+5=2
6х+у-19=2
6х+у=21
11(1+х)-9(7-у)=-36
11+11х-63+9у=-36
11х+9у-52=-36
11х+9у=16
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<span>sin*π/21⋅cos*2π/7+cos*π/21⋅sin*2/π7=sin(</span>π/21+2π/7)=sin(π/21+6π/21)= sin(π/3)=√3/2