Question

5) x - 4y = 28
-4x - y = 7
Solve each system by elimination

Answer 1

(0,-7)

Explanation:

x-4y=28 multiply by 4

-4x-y=7 multiply by 1

4x-16y=112

-4x-y=7

cross out the x and add the rest

-17y= 119

divide by -17

y= -7

now you substitute the y in one of the equations.

the reformed equations

we will use the second one

-4x-(-7)=7

two negative becomes a plus

-4x+7=7

now you minus the 7 to both sides

-4x=0

now divide by -4

x=0

(0,-7)

Answer 2

x = 0, y = -7

Explanation:

x - 4y = 28

-4x - y = 7

____________

x - 4y = 28

-16x - 4y = 28

____________ _

17x = 0

x = 0

0 - 4y = 28

y = -7