Question

пожалуйста помогите
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Answer 1

Ответ:

1){х+2у=7

{3х-4у=11

{х=7-2у

{3(7-2у)=11

{х=7-2у

{21-6у=11

{х=7-2у

{-6у=11-21

-6у=-10|×(-1)

6у=10

у=10/6

у=5/3

у=1целая 2/3

х=7-2×5/3

х=7-10/3

х=7-3целых 1/3

х=3целых 2/3

2){х+у=7

{2х+у=8

{х=7-у

{2(7-у)+у=8

{х=7-у

{14-2у+у=8

{х=7-у

{14-у=8

{х=7-у

{-у=8-14

-у=-6

у=6

х=7-6

х=1

3){у=х+3

{6х+5у=-7

{у=х+3

{6х+5(х+3)=-7

6х+5х+15=-7

11х=-7-15

11х=-22

х=-22:11

х=-2

у=-2+3

у=1

4){х-5у=25

{5х+3у=13

{х=25+5у

5(25+5у)+3у=13

125+25у+3у=13

28у=13-125

28у=-112

у=-112:28

у=-4

х=25+5×(-4)=25-20=5