S=b1·(1- q^n)/(1-q)
n=7
S = 3·(1-3^7)/(1-3) =3·(1-2187) / (-2) = 3279
P - Q = (1/3х - 1/3y) - (x+2y) - (1/3x + 1/3y - (x-y)) =
= 1/3x-1/3y -x -2y -1/3x -1/3y +x -y = x*(1/3-1-1/3+1) - y(1/3+2+1/3+1)=
= -3 2/3 y
А)21х²-7х+3х-1-21х²=3
-4х=4
х=4:(-4)
х=-1
б)1-3х-4х+12х²=12х²-6х
1-3х-4х+12х²-12х²+6х=0
-х=-1
х=1
5cos^2x-sinxcosx=2 5cos^2x-sinxcosx-2(sin^2x+cos^2x)=0
5cos^2x-2cox^2x-sinxcosx-2sin^2x=0 3cos^2x-sinxcosx-2sin^2x=0 делим на cos^2x
3-sinx/cosx-2sin^2x/cos^2x=0 3-tgx-2tg^2x=0 2tg^2x+tgx-3=0 D=1+4*2*3=25 VD=-5 tgx1=-1-5/4=-6/4=-3/2=-1.5 tgx2=-1+5/4=1
x1=arctg(-1.5) x2=pi/4+pin
0.66/1.2=0.55
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