Question

9x−9y=0 3x−4y=10 solve by elimination

Answer 1

Answer:

(-10,-10)

Step-by-step explanation:

9x-9y=0

3x-4y=10

In elimination, we want both equations to have the same form and like terms to be lined up.  We have that.  We also need one of the columns with variables to contain opposites or same terms. Neither one of our columns with the variables contain this.  

We can do a multiplication to the second equation so that the first terms of each are either opposites or sames. It doesn't matter which.  I like opposites because you just add the equations together. So I'm going to multiply the second equation by -3.

I will rewrite the system with that manipulation:

9x-9y=0

-9x+12y=-30

----------------------Add them up!

0+3y=-30

     3y=-30

       y=-10

So now once you find a variable, plug into either equation to find the other one.

I'm going to use 9x-9y=0 where y=-10.

So we are going to solve for x now.

9x-9y=0 where y=-10.

9x-9(-10)=0  where I plugged in -10 for y.

9x+90=0  where I simplified -9(-10) as +90.

9x     =-90 where I subtracted 90 on both sides.

x=       -10 where I divided both sides by 9.

The solution is (x,y)=(-10,-10)