(900-400)+500=1000
900-400+500=1000
(700-400)+500=800
239,247,255,<span>263,271 :)</span>
(1/9)^x-(6/18)^x-27<=0; 6/18=1/3
(1/9)/(1/3)-27<=0;
(1/9)/(3/1)-27<=0;
3/9-27<=0;
1/3-27<=0; |:3
1-9<=0;
-8<=0;
[-8;0]
____________-8\\\\\\\\\\\0______>x
Ответ:[-8;0]
<span>40450/х=7621-7571
</span><span>40450/х=50
</span>
<span>40450=50х
</span>
x= 809
Проверка
40450/809=7621-7571
50=50