The adition method for 2a+3b=-1 and a-3b=4?

Answer 1

2a+3b=-1
a-3b=4
=======
3a=3
a=1

1-3b=4
-3b=3
b=-1

The solution set is (1,-1)

Check:
2(1)+3(-1)=-1
2-3=-1
-1=-1

1-3(-1)=4
1+3=4
4=4

I hope this helps!

Answer 2

2a + 3b = -1
+ a - 3b = 4
--------------------
3a + 0 = 3
a = 3/3
a = 1

Substituting for a and solving for b
2(1) + 3b = -1
2 + 3b = -1
3b = -1 - 2
3b = -3
b = -3/3
b = -1

Substituting and verifying
a - 3b = 4
1 - 3(-1) = 4
1 - -3 = 4

2a + 3b = -1
2(1) + 3(-1) = -1
2 + -3 = -1

a = 1, b = -1

Answer 3

2a+3b=-1
a - 3b = 4
You should be able to see that when you add the two equations, the 3b terms disappear and you are left with:
a+2a = -1 +4
3a = 3
a=1
Now put a =1 in the 2nd equation getting:
1-3b=4
-3b= 3
b=-1

Answer 4

2a + 3b = -1
+ a - 3b = 4
------------------
3a + 0b = 3
3a = 3

First: isolate "a" on one side > divide both terms by "3"...

3a/3 = 3/3
a = 1

Sec: replace "1" with the "a-variable" (either equation) in the 1st equation...

2(1) + 3b = -1
2 + 3b = -1

*Subtract "2" from both sides...

2 - 2 + 3b = -1 - 2
3b = -3

Third: isolate "b" on one side > divide both terms by "3"...

3b/3 = -3/3
b = -1

Solution: (1,-1)

Answer 5

add the equations together:
2a+3b=-1
a-3b=4
3a+0b=3
a=1
Now put 1 in the equation for a
2(1)+3b=-1
3b=-3
b=-1

Answer 6

Add the second equation to the firt and get 3a=3, from which you can determine that a=1. Next substitute a=1 into either of the above equations to get b=-1.