Объяснение:

1)

{х+у=4 у=4-х

{3х+у=6

3х+4-х=6

2х=6-4

2х=2

х=2:2

х=1

у=4-1

у=3

(1;3)

3)

{3р-7q=0

{2p+9q=41

{3p=7q p=7/3•q

{2p+9q=41

2(7/3•q)+9q=41

14/3•q+9q=41

41/3•q=41

q=41:41/3

q=41•3/41

q=3

p=7/3•3=7

(p;q)=(7;3)

2)

{8x-5y=41

{4x+3y= -7

{8x=41+5y

{4x+3y= -7

x=41/8+5/8•y

4(41/8+5/8•y)+3y= -7

41/2+5/2•y+3y= -7

11/2•y= -7-41/2

11/2•y= -55/2

y= -55/2:11/2

y= -55/2•2/11

y= -5

x=41/8+5/8•(-5)=41/8-25/8=16/8=2

(2;-5)

{6a-7b=51

{2a+3b= -15

{6a-7b=51

{2a= -15-3b a= -15/2 -3/2•b

6(-15/2-3/2•b)-7b=51

-45-9•b-7b=51

-16b=51+45

-16b=96

b=96:(-16)

b= -6

a= -15/2-3/2•(-6)= -15/2+9=3/2=1,5

(a;b)=(1,5; -6)