1) 8X+3Y=-13
4X-3Y=25
2)4X+6Y=-5
8X+12Y=7
Solve by using the elimination method?
2012-07-10 1:50 pm
回答 (3)
2012-07-10 1:54 pm
✔ 最佳答案
1) Add: 12x = 12x = 1
8 + 3y = -13
3y = -21
y = -7
2) 2[4x + 6y = -5] --> 8x + 12y = -10
-2(4x - 3y = 25] --> -8x + 6y = -50
18y = -60
y = -10/3
4x + 6(-10/3) = -5
4x - 20 = -5
4x = 15
x = 15/4
2012-07-10 1:57 pm
1)
8X+3Y=-13 (1)
4X-3Y=25 (2)
(1) + (2)
12X = 12
X=1, Y= -7
2)
4X+6Y=-5 (1)
8X+12Y=7 (2)
This cannot be right because multiplying (1) by 2 gives 8X+12Y=-10, which is different to (2).
I don't know where the others found a minus sign in problem 2.
8X+3Y=-13 (1)
4X-3Y=25 (2)
(1) + (2)
12X = 12
X=1, Y= -7
2)
4X+6Y=-5 (1)
8X+12Y=7 (2)
This cannot be right because multiplying (1) by 2 gives 8X+12Y=-10, which is different to (2).
I don't know where the others found a minus sign in problem 2.
2012-07-10 1:54 pm
8x + 3y = - 13
4x - 3y = 25
add the two equations to eliminate "y"
12x = 12
x = 1
substitute the value for x to find y: y = - 7
(1, - 7) is the solution set...check in both equations.
one problem at a time
id est
4x - 3y = 25
add the two equations to eliminate "y"
12x = 12
x = 1
substitute the value for x to find y: y = - 7
(1, - 7) is the solution set...check in both equations.
one problem at a time
id est
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