Question

Solve the system of equations using elimination: -8x -9y= -21 and -2x -4y=0.

Answer 1

x=6, y=-3

Explanation:

Elimination is literally the process of eliminating one of the variables through the process of making them the same.

`\left \{ {{-8x-9y=-21} \atop {-2x-4y=0}} \right.`

After looking at this equation, it is evident that x can be eliminated easier than y. Therefore, we will multiply the bottom line by four to make the top and bottom x the same.

`\left \{ {{-8x-9y=-21} \atop {-8x-16y=0}} \right.`

Then, we can eliminate x by subtracting the top equation from the bottom equation.

`-8x-9y-(-8x-16y)=7y\\-21-0=-21\\7y=-21`

Thus, y=-3.

If we insert that back into an equation,

`-2x-4(-3)=0\\-2x+12=0\\-2x=-12\\x=6`

We get x=6.