Solve the following system of equations:

-2x + y = 1
-4x + y = -1

(3, 1)

(-1, 3)

(-1, -3)

(1, 3)

Question

Solve the following system of equations: 

-2x + y = 1
-4x + y = -1

 (3, 1)

 (-1, 3)

 (-1, -3)

 (1, 3)

solomonzelman · Answer

Let's subtract the second equation from the first equation.


           -2x                  + y                =        1
-  
           -4x                  + y                =    -1
      ---------------------------------
    -2x - - 4x             y - y               =    1 - - 1

-2x+4x     +      0    = 1+1
-2x=2
x=-1

solomonzelman · Answer

Can you solve for y?

anonymous · Answer

I don't really understand how.
Can you solve it & show me all of the steps again ?

solomonzelman · Answer

What you are doing is subtract the first equation from the second ok?

anonymous · Answer

Okay so 1 - (-1) = 2.

solomonzelman · Answer

yes 1-(-1) = 1+1 = 2       correct.

now lets subtract  the variable y in the second equation from variable y in the first equation, Ok?

solomonzelman · Answer

y-y =0 correct?   so so far we have  __x  - 0 = 2

anonymous · Answer

But now what..

solomonzelman · Answer

subtract the variable x in the second equation from the variable x in the first equation.

lets write the subtraction out,

-2x  -  (-4x)

anonymous · Answer

I think the answer is (-1,-3) ..
Is that right ?

solomonzelman · Answer

can we first solve the equation, before jumping to the answer?