В этих уравнениях по 2 корня уравнения
Sin(6a+a)/sina - 2cos2a-2cos4a-1=(sin6acosa+cos6asina/sina - 2cos6a) - 2cos2a-2cos4a-1=sin6acosa+cos6asina=2cos6asina/sina - 2cos2a-2cos4a-1=sin6acosa-cos6asina/sina - 2cos2a-2cos4a-1=(sin5a/sina - 2cos4a) - 2cos2a-1= ( sin(4a+a)/sina - 2cos4a) - 2cos2a-1=(sin4acosa+cos4asina/sina - 2cos4a) - 2cos2a-1= sin4acosa+cos4asina-2cos4asin/sina - 2cos2a-1=sin4acosa-cos4asina/sina-2cos2a-1=sin3a/sina-2cos2a-1=(sin(2a+a)/sina=2cos2a)-1=(sin2acosa+cos2asina/sina - 2cos2a) -1=sin2acosa+cos2asina-2cos2asina/sina-1=sin2acosa-cosa-cos2asina/sina-1=sina/sina-1=1-1=0.
1.(7-3х)^2=49-42х+9х^2
2.(6m-n)(6m+n)=36m^2-n^2
3.42ab-(3a+7b)^2=42ab-9a^2-42ab-49b^2=-9a^2-49b^2
4.(m-5n)(m+5n)(5n-1)^2=m^2-25n^2+25n^2+10n+1=m^2+10n+1
5.49m^2+N+36n^2 по формуле (a+b)^2=a^2+2ab+b^2; N=84mn