Need a little help on this?
If the System
-2x - 7y = - 3
-12x - 6y = - 4
is to be solved using the addition method, by what constant should one of the equations be multiplied if the x terms are dropped out?
Now here are the answers that I had to choose from.
-2
1/6
12
2
-6
2007-04-14 18:14:57 · 8 answers · asked by sabrehw J 1 in Science & Mathematics ➔ Mathematics
Oh ok, Brandon.. I just got a little confused, but Now i got what you mean.. thank you so much:)
2007-04-14 18:23:17 · update #1
-6
Since you are going to add the two equations to drop the x terms out, you have to multiply by something that gives a negative coefficient to one of the x terms that is equal to the coefficient of the x term in the other formula.
The only one that does this is -6.
Multiply the first formula by that and you get 12x for the first term, which when added to the -12x in the second equation will give you a zero x and drop that out.
2007-04-14 18:19:46 · answer #1 · answered by xaviar_onasis 5 · 0⤊ 0⤋
If u want to drop out the x terms multiply (2x and 7y with 6) and (12x and 6y with 1). Value comes out to be (12x and 42y) and ( 42x and 6y).
i.e.,
- (2x + 7y) = -3
-( 12x+6y) = -4
The negative sign on both sides get cancelled.
2x + 7y = 3 multiply with 6
12x+6y = 4 multiply with 1
12x + 42y = 18
- 12x + 6y = 4
That comes out
(42y - 6y) = 18 - 4
36 y = 14
y = 14 / 36
Substitute the value of y in any of the above equation and u'll get the value of x-term.
2007-04-15 01:31:23 · answer #2 · answered by indiavision 4 · 0⤊ 0⤋
The answer is - 6.
If you mulitply the first equation by -6, it becomes
(-6) times (-2x - 7y = -3 )
12x + 42y = 18
Note that the sign of the numbers change. REMEMBER that the product of two NEGATIVE numbers is POSITIVE.
Now you can eliminate x
12x + 42y = 18
-12x -6y = -4
_____________
36y = 14
y = 14/36
y = 7/18
2007-04-15 01:34:16 · answer #3 · answered by detektibgapo 5 · 0⤊ 0⤋
what do you multiply by to make the (-2) become a (12)...?
(-6)
so then multiply the entire top equation by (-6),
then:
(12x) + (-12x) will cancel out, and solve for y.
2007-04-15 01:21:52 · answer #4 · answered by back2earth 3 · 0⤊ 0⤋
-2x - 7y = - 3
-12x - 6y = - 4
12x + 42y = 18
36y = 14
y = 7/18
2007-04-15 01:21:02 · answer #5 · answered by John S 6 · 0⤊ 0⤋
as i told you earlier multiply the top one by -6
2007-04-15 01:18:59 · answer #6 · answered by Brandon 3 · 0⤊ 0⤋
-6 then you will have (-2)*(-6) =12
so 12x and -12x will addout
:)
2007-04-15 01:18:45 · answer #7 · answered by Anonymous · 0⤊ 0⤋
-6
Hint:
12x+42y=18
-12x-6y=-4
--------------------------
by adding
36y=14
y=7/18
2007-04-15 01:20:02 · answer #8 · answered by iyiogrenci 6 · 0⤊ 0⤋