1)Умножаем 1 строку на 1/3
2)Прибавляем ко 2 строке 1 строку умноженную на (-2). Прибавляем к 3 строке 1 строку умноженную на (-5).
3)Умножаем 2 строку на (-3/11)
4)Прибавляем к 3 строке 2 строку умноженную на (8/3).
Теперь подставляем полученные значения в систему
Из полученной системы находим данные
6Z=6 (Делим обе части на 6)
Z=1
y-2Z=0
y=2Z
y=2*1
y=2
x+(1/3)*y - (5/3)*Z = - 2
x= -2 -(1/3)*2 + (5/3)*1
x= -2 - (2/3) + (5/3)
x= (-6 - 2+ 5)/3
x= (-3)/3
x=-1
Ответ: x=-1 y=2 Z=1
(y+1)/(y-3) -1=7/y
y(y+1)-y(y-3)=7(y-3)
y²+y-y²+3y-7y+21=0
21=3y
y=7
Х- в день 1,у-в день 2
1/(х+у)=4⇒х+у=1/4⇒у=1/4-х
1/3х+2/3у=10⇒у+2х=30ху
1/4-х+2х=30х(1/4-х)
0,25+х-7,5х+30х²=0
30х²-6,5х+0,25=0
D=42,25-30=12,25 √D=3,5
x1=(6,5-3,5)/60=3/60=1/20⇒y1=1/4-1/20=4/20=1/5
x2=(6,5+3,5)/60=10/60=1/6⇒y2=1/4-1/6=1/12
1)x1=1/20⇒1:1/20=20дней
у1=1/5⇒1:1/5=5дней
2)х2=1/6⇒1:1/6=6дней
у2=1/12⇒1:1/12=12дней
18х-5=6х+21
18х-6х=21+5
12х=26
х=26/12
х=2 2/12
х=2 1/6
<span><span><span>{<span><span>x−y=0
</span><span>4x−5y=8</span></span></span>⇒
</span><span><span>{<span><span>x−y=0
</span><span>4x−5y=8</span></span></span>⇒</span></span><span><span>{<span><span>−y+x=0
</span><span>4x−5y=8
</span></span></span><span>{<span><span>−y+x=0
</span><span>4x−5y=8</span></span></span></span>Решение методом подстановки.<span><span><span>{<span><span>x−y=0
</span><span>4x−5y=8</span></span></span>⇒
</span><span><span>{<span><span>x−y=0
</span><span>4x−5y=8</span></span></span>⇒</span></span><span><span><span>{<span><span>x=y
</span><span>4x−5y=8</span></span></span>⇒
</span><span><span>{<span><span>x=y
</span><span>4x−5y=8</span></span></span>⇒</span></span><span><span><span>{<span><span>x=y
</span><span>4<span>(x)</span>−5y=8</span></span></span>⇒
</span><span><span>{<span><span>x=y
</span><span>4<span>(x)</span>−5y=8</span></span></span>⇒</span></span><span><span><span>{<span><span>x=y
</span><span>−y−8=0</span></span></span>⇒
</span><span><span>{<span><span>x=y
</span><span>−y−8=0</span></span></span>⇒</span></span><span><span><span>{<span><span>x=y
</span><span>y=−8</span></span></span>⇒
</span><span><span>{<span><span>x=y
</span><span>y=−8</span></span></span>⇒</span></span><span><span>{<span><span>x=−8
</span><span>y=−8
</span></span></span><span>{<span><span>x=−8
</span><span>y=−8</span></span></span></span>Ответ:<span>(<span>−8;−8</span><span>)</span></span>