How do you solve this system of equations: -x - 2y = - 4 and 2x - y = 3?

1 Answer
Alok Shukla
Dec 14, 2017

x = 2, y=1

Explanation:

Algebra

2x-y=3

4x-2y=6 -- (i)

-x-2y=-4 -- (ii)

equation i minus equation ii,

(4x-2y) - (-x-2y) = 6-(-4)

4x-2y +x+2y= 10

5x = 10

x = 2

Putting it in equation (i),

4(2)-2y=6

4-y=3

y=1

So, the answer is x = 2, y=1.

Geometry

2x-y=3 => y = 2x-3

-x-2y=-4 => y = -x/2+2

Plotting these lines,

graph{(2x-y-3)(x+2y-4)=0}

These cross each other at (2,1) so the solution to these equations will be x=2, y=1.

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