help with this problem i'm stuck...?
Solve using the elimination method. Show your work. If the system has no solution or an infinite number of solutions, state this.
So this is what i got--- multiply -2 to the first equation gives me -6x+8y=1..... then combine the 2 equation-6x+6y=-3 i get -12x+16y=-2 now what do i do..
Please show work.. thanks you imn advance........
- 9 years agoFavorite Answer
You didn't have to muiltyply the 2nd line by 2...
-6x + 8y=-2 [Muilty the whole thing by -2 even the anwser]
-6x + 6y=-3 [Leave the 2nd eqation alone]
2y=1 [Forget about the xs they now cancel each other out and subtract the rest of the eqation]
y=2 [Divide 2]
TO find the x you subsite the y and pick any of the 2 ORGINAL eqations
3x + 4y =1
3x + 8 =1 [Y=2 times that by the 4]
3x =-7 [Subtract the 8]
x=2.333333333333333333333333333 [Divide by 3]
If you're not sure that you got it right you can plug in both anwsers to see if it's true
-3x + 4y = 1
-7 + 8 = 1 [Substute the x and y vaules and muiltiply I also rounded 6.999999 to 7]
1 = 1 [The values match so I'm right]
- Christophe GLv 49 years ago
multiply by -2 gives you +6x - 8y = -2. Combine and you get 6x - 6x +6y -8y = -2 -3 or -2y = -5 which means y = 5/2. Substitute his value into the first equation and you get -3x + 4*(5/2) = 1 or -3x + 10 = 1
or -3x = -9 which means x = 3.
- 9 years ago
First mult first definition by -2
6x - 8y = -2
-6x+6y = -3
then add or subtract
0x - 2y = -5
y = 2.5
and then -3x + 4(2.5) = 1
-3x + 10 = 1
-3x = -9
x = 3
so answer would be (3, 2.5)
- 9 years ago
what you want to do is eliminate ONE of the variables.
1. Multiply -2 to the first equation -> 6x-4y= -2
2. Then line them up like this: 6x - 4y= -2
-6x+ 6y= -3
3. Add them up. 6x + -6x=0, -4y + 6y= 2y, -2 + -3 = -5
4. the equation that you end up with is: 2y=-5
5. Solve for y.
6. Plug in the number you get for y in the first (or second) equation.
7. Solve for x.
I'm not going to do all of it for you, so you have to do the actual math...Source(s): Knowledge.
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- Anonymous9 years ago
Multiply the first equation by -2.
Then add the two equations.
Then plug in the value of y into either of the two original equations.
Answer: x=3 and y=5/2
- MechEng2030Lv 79 years ago
Multiplying the first eqn by -2 does not give you -6x + 8y = 1.... Please try again.