Question

a)2x-3y=7 3x-5y=11

b)5p-2r=21 3p+5r= -6

Answer 1

a) 2x-3y=7

3x-5y=11

 

2x=7+3y/:2

3x-5y=11

 

x=3.5+1.5y

3(3.5+1.5y)-5y=11

 

x=3.5+1.5y

10.5+4.5y-5y=11

 

x=3.5+1.5y

-0.5y=0.5/:(-0.5)

 

x=3.5+1.5*(-1)

y=-1

 

x=2

y=-1

 

b) 5p-2r=21

3p+5r= -6

 

5p=21+2r/:5

3p+5r=-6

 

p=4.2+0.4r

3(4.2+0.4r)+5r=-6

 

p=4.2+0.4r

12.6+1.2r+5r=-6

 

p=4.2+0.4r

6.2r=-18.6/:6.2

 

p=4.2+0.4*(-3)

r=-3

 

p=3

r=3

 

 

 

 

Answer 2

a.]

2x-3y=7 | * (-3)
3x-5y=11 | * 2

-6x + 9y = -21
6x - 10y = 22



9y - 10y = -21 + 22
-y = 1 | * (-1)
y = -1


2x - 3 * (-1) = 7
2x + 3 = 7
2x = 4 | /2
x = 2


x = 2
y = -1 liczę na naj.