Х1*х2=-18
х2=-18/9=-2
х1+х2=р
р=9-2=7
<span>1){x+y=2 {x=2-y {x=2-y {x=2-y {x=2 </span>
<span>{3x-2y=6 {6-3y-2y=6 {-5y=0 {y=0 {y=0</span>
Ответ:<span>(2:0)</span>
<span>2){<span>y=3x {<span>y=3x </span></span></span>
<span><span><span> {x+y=4 {</span></span></span>y=4-x
3){<span>x-y=1 {x=1+y {x=1+y {x=6</span>
<span> {x-3y=-9 {1+y-3y=-9 {2y=10 {y=5</span>
<span>(6;5)</span>
<span>Ответ: одно решение</span>
Ctg(2π-5π/13)=-ctg5π/13
cos(3π-π/3)=cos(π-π/3)=-cosπ/3=-1/2
2,5x=-7,5
х=-7,5/2,5
х=-3
3x-13,5=0
3х=13,5
х=13,5/3
х=4,5
4y+2=8+5y
2-8=5у-4у
у=-6
|x+5|=6
х=6-5
х=1
Х+2х+90+2х=360
5х=270
х = 54