solving by elementaion

Question

 

 

3x+y=2

3x+2y=7 

Answer 1

Timo, I assume you mean elimination.  What we can do is add any two equations together.  In this case, if we did so, we'd get 6x + 3y = 9.

 

But, we want to get rid of one of the variables when we add.  Remember that, say, 7x + (-7x) = 0.  Remember also that we can multiply an equation by anything and the graph stays the same.

 

So, we have

 

3x +  y = 2

3x + 2y = 7

 

We already said that 3x + 3x = 6x, buuuuut 3x + (-3x) = 0.  We can multiply either equation by -1.  Let's try the second.

 

Now, we have

 

 3x +  y = 2

-3x - 2y = -7.

 

If we add these, we get 0 - y = -5, so y = 5.

 

Now, take your value for y, plug in into either equation to find your value for x.

 

Hope this helps!

Answer 2

Since the coefficient of the x variable each being 3 in the two equations you could simply eliminate the x variable by subtracting the two equations in which is:

 

3x-3x+y-2y=2-7

 

Hence, -y=-5 Thus, y=5

 

Now, substitute y=5 in one of the equations to solve for x. I would substitute y=5 in the first equation in which is:

 

3x+5=2

 

I'll let you take it from here.