Question 29229: can someone show me how to solve by addition method...
2x=2-y
3x+y=-1
Answer by sdmmadam@yahoo.com(530)   (Show Source):
You can put this solution on YOUR website! can someone show me how to solve by addition method...
2x=2-y ----(1)
3x+y=-1 ---(2)
Rewriting (1)
(LHS = RHS same as RHS = LHS)
(Tom's age = Jack's age same as Jack's age = Tom's age)
2-y = 2x ---(3)
(2) +(3)
(3x+y)+(2-y)=(-1)+(2x)
3x+2+(y-y) =-1+2x
3x+2+0 = -1+2x
(3x-2x) = -1-2 (grouping like terms, change side then change sign)
x = -3
Put x=-3 in (2)
3x+y=-1
3X(-3)+y = -1
-9+y =-1
y =-1+9 = 8
Answer: x=-3,y=8
Verification: x=-3,y=8 in (1)
LHS = 2x= =2X(-3) = -6 = 2-8 = 2-y = RHS
Therefore our values are correct.
Note: Addition includes subtraction.
Observe that (1) is 2x+y = 2 ---(*) (bringing y from the right to the left)
And (2) is 3x+y=-1 ---(2)
(*)-(2) implies (2x-3x)+0 = 2-(-1)
-x = 3 giving x=-3
and then proceed as above
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