Ответ:
-2y+x
Объяснение: -4x+y+5x-3y=x(-4+5)+y(1-3)= x(1)+y(-2)=x+(-2y)=x-2y
<span>cos17cos73=0.5(cos90+cos56)</span>
<span><span>sin13cos21=0.5(sin34-sin8)</span></span>
<span><span><span>cos4cos86=0.5(cos90+cos82)</span></span></span>
<span><span><span>cos90=0</span></span></span>
<span><span><span>cos56=cos(90-34)=sin34</span></span></span>
<span><span><span>cos82=cos(90-8)=sin8</span></span></span>
<span><span><span><span>cos17cos73-sin13cos21-cos4cos86=0.5(sin34-sin34+sin8-sin8)=0</span></span></span></span>
<span>2a -( 14-3a)=-10
5а-4=0
а=0,8
</span>(9-2b)-(b+5)=16
-3b-12=0
b=-4