SOLUTION: Solve each system of linear equations by either substitution or by adding equations. x + y = −5 3x − 4y = 6

Question 1133558: Solve each system of linear equations by either substitution or by adding equations.

x + y = −5
3x − 4y = 6
Found 3 solutions by Alan3354, addingup, MathLover1:
Answer by Alan3354(69443)   (Show Source): You can put this solution on YOUR website!
Multiply the 1st equation by 4, then add.
========
Or, multiply the 1st equation by -3, then add.

Answer by addingup(3677)   (Show Source): You can put this solution on YOUR website!
x + y = −5, x = -5-y
3x − 4y = 6
substitution:
3(-5-y) -4y = 6
-15-3y-4y = 6
-7y = 21
y = -3
and x = -5-(-3) = -2
Check:
x + y = -5
-2 + -3 = -5 Correct
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
addition:
x + y = −5 multiply all times -3 and add to the next equation
3x − 4y = 6
.
-3x +- 3y = 15
+
3x - 4y = 6
-----------------
0x - 7y = 21
y = -3 of course, same answer as you get by substitution. Solve for x and you'll find it comes out to -2.
.
Happy learning
Answer by MathLover1(20850)   (Show Source): You can put this solution on YOUR website!
.......eq.1
.......eq.2
--------------------------------------
start with
.......eq.1...solve fo
.....eq.1a..substitute in eq.2

.......eq.2 ..solve fo

go back to eq.1a, substitute
.....eq.1a

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