Question

Помогите решить примеры #4 2,7,8 примеры!

Answer 1

Объяснение:

2.

2(x+y)=(x-y)+5

3(x+y)=(x-y)+8

3(x+y)-2(x+y)=x-y+8-x+y-5

x+y=3

x=3-y

2(3-y+y)=(3-y-y)+5

2•3=3-2y+5

8-2y=6

4-y=3

y=4-3=1

x=3-1=2

(2; 1)

7.

4x-9y=-24

2x-y=2

y=2x-2=2(x-1)

4x-9•2(x-1)=-24

2x-9x+9=-12

9-7x=-12

7x-9=12

7x=12+9

x=21/7=3

y=2(3-1)=2•2=4

(3; 4)

8.

5x+4y=13

3x+5y=13

5x+4y-3x-5y=13-13

2x-y=0

у=2х

3х+5•2х=13

3х+10х=13

13х=13

х=13/13=1

у=2•1=2

(1; 2)