D=(60,6-61,8)/3=-0,4
a4=a1-0,4(n-1)
61,8=a1-1,2
a1=63
S7=n(a1-0,4(n-1))/2
S7=7*(63-2,4)/2
S7=212,1
5a-(a+1)(4a+1)=5a-(4a²+a+4a+1)=5a-4a²-a-4a-1=5a-4a²-5a-1=-4a²-1
2x+y=5
4x+2y=7
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y=5-2x
4x+2(5-2x)=7
----------------------
y=5-2x
4x+10-4x=7
------------------
y=5-2x
0.x=-3
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Prjamye paralelny, ne perecekajutsja.
<span>sin^2 (18)-cos^2(18)=-cos(36)=-cos(90-54)=-sin(54). Это числитель.</span>
<span>sin^2 (117)=sin^2 (90+27)=сos^2 (27)</span>
<span>10*tg(27)*сos^2 (27)=10sin (27)сos(27)=5sin(54). Это знаменатель.</span>
<span>(-sin(54))/(5sin(54))=-1/5</span>