Roziąż układy równań metodą podstawiania.
a) { x+3y=3
{ x-y=5
b) { 2x-y=10
{ x+5y=-17
c) { 3m+n=9
{ 2m-5n=-11
d) { 4a-2=b
{ 3a+7b=1,5
e) { 5x=4-2y
{ 4x+y=3
f) { 6x-3y=9
{ x+5y=-9,5
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a)
{ x+3y=3
{ x-y=5 => x=5+y
{ 5+y+3y=3
{ x=5+y
{4y=-2|:4
{x=5+y
{y=-(1/2)
{x=5-1/2
odp. {x=4 i 1/2 ; y=-1/2
b)
{ 2x-y=10
{ x+5y=-17 => x=-17-5y
{2(-17-5y)-y=10
{x=-17-5y
{-34-10y-y=10
{x=-17-5y
{-11y=44 |:(-11)
{x=-17-5y
{y=-4
{x=-17-5*(-4)=-17+20=3
odp.{x=3 ; y=4
c)
{ 3m+n=9 => n=9-3m
{ 2m-5n=-11
{ 2m-5(9-3m)=-11
{n=9-3m
{2m-45+15m=-11
{n=9-3m
{17m=34 |:17
{n=9-3m
{m=2
{n=9-3*2=9-6=3
odp {m=2 ; n=3
d)
{ 4a-2=b
{ 3a+7b=1,5
{3a+7(4a-2)=1,5
{ 4a-2=b
{3a+28a-14=1,5
{ 4a-2=b
{31a=15,5 |:31
{ 4a-2=b
{a=1/2
{ b=4*(1/2)-2=0
odp.{ a=1/2 ; b=0
e)
{ 5x=4-2y
{ 4x+y=3 => y=3-4x
{5x=4-2(3-4x)
{y=3-4x
{5x=4-6+8x
{y=3-4x
{-3x=-2 |:(-3)
{y=3-4x
{x=2/3
{y=3-4*(2/3)=3-2 i 2/3=1/3
odp {x=2/3 ; y=1/3
f)
{ 6x-3y=9
{ x+5y=-9,5 => x=-9,5-5y
{6(-9,5-5y)-3y=9
{x=-9,5-5y
{-57-30y-3y=9
{x=-9,5-5y
{-33y=66 |: (-33)
{x=-9,5-5y
{y=2
{x=-9,5-5*2=-9,5-10=-19,5
odp. {x=-19,5 ; y=2