solve this system of equations

Question

x+3y=-5

9x+30y=-48

Answer 1

You can solve by substitution or by elimination. I prefer substitution, but it is up to you how to do it. Let me show you how I think about the problem.

 

I see that we can easily solve for X in the first equation, so I would do

 

X = -5 -3y

 

which is pretty straightforward. The next step is to substitute that X into the next equation.

 

9 (-5 - 3y) +30y = -48       distribute the 9

-45 - 27y + 30y = -48      group the y terms

-45 + 3y = -48                  get the y term by itself by adding 45 to both sides

3y = -3                             divide by 4 to solve for y

y = -3/3 =-1

 

Now plug this Y value back into the equation where we solved for X before the substitution.

x = -5 -3(-1)

   = -5 + 3

x = -2

 

I hope this helps!

Answer 2

many ways to go about it, for example, starting out by multiplying first equation by -10:

-10x - 30y = 50
9x + 30y = -48

Now add the two equations together:

-10x + 9x -30y + 30y = 50 - 48
-x = 2
x = -2

Plug x = -2 into the original first equation:
x + 3y = -5
-2 + 3y = -5
3y = -3
y = -1

x = -2, y = -1

Answer 3

Hi Katie,

 

x+3y=-5
9x+30y=-48

 

multiply the first equation by 10

 

10x+30y=-50
9x+30y=-48

 

Subtract the second equation from the first

 

x=-2

 

x+3y=-5
-2+3y=-5

3y=-5-(-2)

3y=-3

y=-1

 

So, x= -2, and y=-1

 

I hope it helps

A