Answer:
A) 3x - y = -5
B) x + 4y = 7
Whenever you have to solve for 2 unknowns, you need 2 equations. (These are called solving simultaneous equations.)
Perhaps the easiest way to solve these is by the elimination of variables.
Looking at Equation A) we see that if we multiply it by 4, and add it to equation B), the "y" variable will be eliminated.
Multiplying equation A) by 4 we get
A) 12x - 4y = -20 then adding this to B)
B) x + 4y = 7 we get
EDITD TO CORRECT**************************************************
13x = -13
x = -13 / 13= -1
Then we can get x = -1 and insert it into either equation. (Let's choose B)
B) -1 + 4y = 7
B) 4y = 8
y = 2
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For a double-check we can insert x = -1 and y = 2 into either equation. (Let's choose equation B)
B) -1 + 4 * 2 = 7
B) -1 + 8 = 7
And since -1 + 8 DOES equal 7, we know that we have solved for "x" and "y" correctly!
Source:
https://en.wikipedia.org/wiki/System_of_linear_equations
Elimination of variables
Step-by-step explanation:
