how do I do this problem?
回答 (13)
2008-12-29 3:29 am
✔ 最佳答案
2x+y=7 x-4y=4x=4+4y
2(4+4y)+y=7
8+8y+y=7
8+9y=7
9y=7-8
9y=-1
y=-1/9
finding the value of x
x=4+4y
x=4+4(-1/9)
x=4-4/9
x=32/9 answer @(^_^)@
2008-12-29 11:19 am
solve for x in terms of y or solve for y in terms of x. I'll solve for y in terms of x b/c its harder.
2x+y=7 is the same as y=7-2x
x-4y=4 is the same as x-4(7-2x)=4
x-28+8x=4
9x=32
x=32/9
plug it in either equation to solve for y.
2(32/9)+y=7
64/9+y=7
y= - (1/9)
2x+y=7 is the same as y=7-2x
x-4y=4 is the same as x-4(7-2x)=4
x-28+8x=4
9x=32
x=32/9
plug it in either equation to solve for y.
2(32/9)+y=7
64/9+y=7
y= - (1/9)
參考: got an 800 on my math SAT
2008-12-29 11:17 am
Multiply the first equation by 4
8x + 4y = 28
Now add this to the second equation
8x + 4y + (x - 4y) = 28 + 4
9x =32
x = 32/9 = 3.56
8x + 4y = 28
Now add this to the second equation
8x + 4y + (x - 4y) = 28 + 4
9x =32
x = 32/9 = 3.56
2008-12-29 11:16 am
in both problems make the x equal to each other so 2x + y = 7 and 2x - 8y = 8 then put the first ontop of the other and subtrack so 0x + 9y = -1 so y eqaul -1/9 then put that in for y in one of the problems and solve for x
2008-12-29 11:15 am
im in 9th grade math so what i got was
x+y=3.5 and x-y=0
idk if thats right
x+y=3.5 and x-y=0
idk if thats right
2008-12-29 11:15 am
2x + y = 7
x - 4y = 4
Using the top equation and basic algebra manipulation, we'll rearrange it to get y by itself:
y = 7 - 2x
Now, replace the y in the bottom equation with 7 - 2x so:
x - 4y = 4 â x - 4(7 - 2x) = 4
x - 4(7 - 2x) = 4
x - 28 + 8x = 4
9x - 28 = 4
9x = 32
x = 32/9
x - 4y = 4
Using the top equation and basic algebra manipulation, we'll rearrange it to get y by itself:
y = 7 - 2x
Now, replace the y in the bottom equation with 7 - 2x so:
x - 4y = 4 â x - 4(7 - 2x) = 4
x - 4(7 - 2x) = 4
x - 28 + 8x = 4
9x - 28 = 4
9x = 32
x = 32/9
2008-12-29 11:14 am
Multiply the first eqn. by 4:
8x + 4y = 28
x - 4y = 4
Add straight down: 9x = 32, so x = 32/9
32/9 - 4y = 4
32 - 36y = 36
-36y = 4
y = -4/36 = -1/9
(32/9, -1/9) is the result.
8x + 4y = 28
x - 4y = 4
Add straight down: 9x = 32, so x = 32/9
32/9 - 4y = 4
32 - 36y = 36
-36y = 4
y = -4/36 = -1/9
(32/9, -1/9) is the result.
2008-12-29 11:13 am
abc
2x + y =7
x -4y = 4
adding down method.
multiply the top equation by 4 to cancel out the Y. -4y + 4y = 0
making it 8x +4y = 32
x-4y = 4
add down like values
9x = 36
x = 4
put this back to any equation you like.
2(4) + Y = 7
Y = -1
X= 4
2x + y =7
x -4y = 4
adding down method.
multiply the top equation by 4 to cancel out the Y. -4y + 4y = 0
making it 8x +4y = 32
x-4y = 4
add down like values
9x = 36
x = 4
put this back to any equation you like.
2(4) + Y = 7
Y = -1
X= 4
2008-12-29 4:06 pm
2x + y = 7 (solve by using elimination)
x - 4y = 4
2x + y = 7
4(2x + y) = 4(7)
8x + 4y = 28
...8x + 4y = 28
+) x - 4y = 4 (addition)
----------------------------
9x = 32
9x = 32
x = 32/9
â´ x = 32/9
x - 4y = 4
2x + y = 7
4(2x + y) = 4(7)
8x + 4y = 28
...8x + 4y = 28
+) x - 4y = 4 (addition)
----------------------------
9x = 32
9x = 32
x = 32/9
â´ x = 32/9
2008-12-29 11:58 am
Using elimination:
2x + y = 7.......equ1...multiply by 4
8x + 4y = 28.....equ1
..x .- 4y = 4
------------------------.....now add together
9x = 32......divide both sides by 9
x = 32/9........answer
2x + y = 7.......equ1...multiply by 4
8x + 4y = 28.....equ1
..x .- 4y = 4
------------------------.....now add together
9x = 32......divide both sides by 9
x = 32/9........answer
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