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<span>y - скорость теплохода </span>
<span>a - скорость течения </span>
<span>120/(y-a)=5 </span>
<span>180/(y+a)=6 </span>
<span>5y-5a=120 </span>
<span>6y+6a=180 </span>
<span>y-a=24 </span>
<span>y+a=30 </span>
<span>просуммируем 2 уравнения, получим: </span>
<span>2x=54 </span>
<span>x=27 -> y=3</span>
=)
13а -15а -4+1,8 = -2а -2,2=-2(а +1,1).
Cos(4x-2x)>0.5
cos2x>0.5
2πn+π/3 > 2x>-π/3+2πn
π/6+πn> x>-π/6+πn
(m/(m-n)-m/(m+n)):16m³n/(m²-n²)=(m²+mn-m²+mn)/(m²-n²)*(m²-n²)/16m³n=2mn/16m³n=1/8m²