<span> 1/6*(12c-2a) - 2/3*(a-3c)=2с-1/3а-2/3а+2с=-1а. ВРОДЕ ТАК:)))</span>
Sinxcosx+cos^2x-1>0
sinxcosx+cos^2x-cos^2-sin^2x>0
sinxcosx-sin^2x>0
sinx(cosx-sinx)>0
sinx>0 Пk<x<П+Пk
tgx<1 -П/2+Пk<x<П/4+Пk
2Пk<x<П/4+2Пk
sinx<0
tgx>1
5П/4+2Пk<x<3П/2+2Пk
2Пk<x<П/4+2Пk U 5П/4+2Пk<x<3П/2+2Пk
(b-4)(b+4)-(b²-6)=b²-16-b²+6=-10
(1-z)(1-z)=1-z-z+z^2=10(1-2x+z^2)+20z=10-20z+10z^2+20z=10-10z^2=10(1-z)^2
3х-4у=-12
При х=7
3*7-4у=-12
21-4у=-12
-4у=-12-21
-4у=-33
у=-33\-4
у= 8,25