Question

a)

b)

c)

Answer 1

a)

x+4y=1

x-8y=-1 / *(-1)

 

x+4y=1

-x+8y=1

 

12y=2 /:12

y=2/12 = 1/6

x+4*1/6=1

x=

 

 

Answer 2

a)

x+4y=1  / * 2

x-8y=-1

 

2x+8y=2

x-8y=-1

..............

3x=1

x=1/3

 

x+4y= 1

1/3+4y=1

4y=1-1/3

4y=2/3

y=1/6

 

b)

6x-9y=6  / * (-4)

8x-5y=7/3   /*3

 

-24x+36y=-24

24x-15y=7

...............

21y=-17

y=-17/21

 

6x-9y=6

6x-9 * (-17/21)=6

6x=6-7  2/7

6x=-1  2/7

x=- 9/7 * 1/6=- 3/14

 

x=-3/14

y=-17/21

 

c)

2x-y=1

3(2x-y)-4(1-x)-3y=1

 

2x-y=1

6x-3y-4+4x-3y=1

 

2x-y=1  / * (-5)

10x-6y=5

 

-10x+5y=-5

10x-6y=5

................

-y=0

y=0

 

2x-y=1

2x-0=1

2x=1

x=1/2

 

x=1/2

y=0