solving systems using the elimination method

Question

2s+1t = -3

-2s-3t=-7

solve using the elimination method.  I know the answer is s(-4), t(5) I just can figure out how to get that?  I need a step by step answer.

Answer 1

2s+1t = -3
-2s-3t=-7

 

In solving systems of equations, you want to simplify down to an equation with only variable that can be solved.  In the above two equations, one contains a +2S term and the other a -2S term, so let's add them to eliminate the s variable:

 

 2s + 1t = -3

-2s -  3t = -7

---------------

0   - 2t   = -10

 

We are left with:

 

-2t = -10

 

Divide both sides by -2 to get:

 

t = 5

 

Now plug t = 5 into either original equation and solve for s:

 

2s + 1t = -3                  [The first equation in the problem]

2s + (1*5) = -3             [Plugged in t = 5]

2s + 5 = -3

2s = -8                         [Subtract 5 from both sides, then divide by 2]

 

s = -4