2cos^2 x +14cos x=3sin^2 x
2cos^2 x+14cos x-3*(1-cos^2 x)=0
2cos^2 x+14cos x-3+3cos^2 x=0
5cos^2 x+14cos x-3=0
cos x=t; 5t^2+14t-3=0; D1=7^2-5*(-3)=49+15=64=8^2; t1=(-7-8)/5=-3;t2=1/5;
cos x=-3 ili cos x=0,2
решений нет x=+-arccos0,2+2πn; n-celoe
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7 14/15+2 1/5=7+2+14/15+1/5=9+(14+1*3)/15=9 17/15=10 2/15
9 24/27+12 13/27=9+12+ (24+13)/27=21 37/27=22 10/27
1-12/19=19/19-1/19=(19-12)/19=7/19
8-3 6/15=8-3-6/15=5-6/15=4 15/15-6/15=4 (15-6)15=4 9/15=4 3/5
12/11-6/11=(12-6)/11=6/11
U1= 14,4 км/ч
t1= 0,6 ч.
t2= 0,4ч
U2=?
Решение
S= U × t.
S=14,4×0,6=8,64км.
U2= S/t2
U2= 8,64÷0,4=21,6км/ч.
<span>68+х-6=164
</span><span>х=164-68+6
</span>х=102
Проверка:
68+102-6=164
BC=у-7,35
CD=у+51,2
ABCD=у+у-7,35+у+51,2=3у+43,85