Solve the system by graphing.
3x + y = –1
9x + 3y = –3
Solve the system by addition.
5x – 4y = –5
x – 2y = –7
Solve the system by addition.
2x – 4y = 7
4x + 2y = 9
2006-10-23 11:16:42 · 2 answers · asked by Ash1227 2 in Science & Mathematics ➔ Mathematics
Solve the system by graphing.
3x + y = –1
9x + 3y = –3
You have to do the graphing yourself. Just be careful and note the coordinate at which the two lines intersect.
Solve the system by addition.
5x – 4y = –5
x – 2y = –7
This is more easily done by subtraction, but addition follows.
Multiply the second equation by -2
-2x + 4y = 14
Add this to the first equation
3x = 9
x = 3
Use this result in the first equation
5(3) - 4y = -5
15 - 4y = - 5
- 4y = - 20
y = 5
Test in the second equation
3 - 2(5) = -7
3 - 10 = - 7
-7 = - 7
Solve the system by addition.
2x – 4y = 7
4x + 2y = 9
Here you can either multiply the first equation by 2 or the second equation by 2 before adding. Then proceed as above.
2006-10-23 11:29:55 · answer #1 · answered by Anonymous · 0⤊ 0⤋
To solve a system of equations by addition you need to multiply one of the equations by some number so that when you add them together one of the unknown variables will be eliminated. Lets take the middle problem. If we multiply the bottom equation by -2 it will work.
-2 * (x - 2y = -7)
-2x - (2*-2)y = -7 * -2
-2x + 4y = 14
Okay, now we add the first equation to this one.
-2x + 5x + 4y - 4y = 14 - 5
The y's cancel so
3x = 9
x=3
Then go back and substitute x = 3 into either of the original equations to find y.
2006-10-23 18:33:47 · answer #2 · answered by Geoffrey S 3 · 0⤊ 0⤋