first method: substitution
x+y=4
x=4-y---------1
x-y=10
x=10+y-------2
substitute 1-->2
4-y=10+y
-2y=6
y=6/-2
y=-3
second method: elimination
x+y=4-------1
x-y=10------2
minus 2 by 1
x+y=4
(-) x-y=10
------------->x-x=0, y-(-y)=2y, 4-10=-6
2y=-6
y=-6/2
y=-3
moreover, you can use back one out of two of the equation to find x when y=-3.
eg. when y=-3
x+y=4
x+(-3)=4
x=7
2006-08-20 17:32:09
·
answer #1
·
answered by Marushka 2
·
0⤊
1⤋
7
2006-08-21 00:22:42
·
answer #2
·
answered by Neutro 4
·
0⤊
0⤋
x + y = 4
x - y = 10
-----------
2 x + y - y = 4 + 10 (y -y = 0)
2 x = 14 ==> x = 7
7 + y = 4 ==> y = 4 - 7 = - 3
S= {x = 4; y = -3}
2006-08-22 06:05:41
·
answer #3
·
answered by bebevampire 2
·
0⤊
0⤋
x=-3
first you have to set it up to find y with the information that you already know.
x-y=10, so x=10+y
and then put that value of x into the first equation,
(10+y)+y=4 ---> 10+2y=4--> 2y=-6--> y=-3
(and x=7)
2006-08-21 00:25:56
·
answer #4
·
answered by sm2shakedown 2
·
0⤊
0⤋
x+y=4
x=4-y
therefore (4-y) - y = 10
so 4 - 2y = 10
-2y= 6
- y = 3
therefore y = -3
2006-08-21 00:24:31
·
answer #5
·
answered by michael2003c2003 5
·
0⤊
0⤋
make x-y=10 with one variable.
x=y+10
plug that in x+y=4
(y+10)+y=4
2y+10=4
-10 =-10
2y=-6
y=-3
plut that in the first eqution.
x-(-3)=10
x+3=10
x=7
2006-08-21 00:24:47
·
answer #6
·
answered by gnomef0cker 3
·
0⤊
0⤋
use elimination method
2x = 14
then get x = 7,
substitute to one of the equations
7 + y = 4
transpose 7 then y =-3
2006-08-21 01:48:22
·
answer #7
·
answered by -xue- 3
·
0⤊
0⤋
x+y=4
x-y=10
When you combine them (addition), the y's cancel out so you're left with:
2x = 14
Divide both sides by 2:
x=7
Plug it into the original equation:
7+y=4
Subtract 7 from both sides:
y=-3
Check with the equations:
x+y=4
7+(-3)=4
4=4
x-y=10
7-(-3)=10
10=10
2006-08-21 00:29:07
·
answer #8
·
answered by Anonymous
·
0⤊
0⤋
Solve one your equations for x or y.
x-y =10
add y to both sides
x=10+y
now you can substitute your new value for x in the other equation.
10+y +y = 4
10 +2y =4
subtract 10 from both sides
2y = -6
divide by 2
y = -3
Hope that helps.
2006-08-21 00:23:44
·
answer #9
·
answered by goodlittlegirl11 4
·
0⤊
0⤋
y=-6
2006-08-21 00:22:17
·
answer #10
·
answered by aznxpranksta69 4
·
0⤊
0⤋