Can someone please help me with this. I keep getting x=1.85 and I know that is wrong so I am missing astep somewhere
Solve the system by addition
-4x+7y= -10
x-5y=9
Thank you all in advance for your time and help!!!
2007-01-08 18:09:14 · 6 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
-4x+7y=-10
x-5y=9
multiply the bottom by 4
-4x+7y=-10
4x-20y=36
---------------
-13y=26
divide by -13
y=-2
2007-01-08 18:18:44 · answer #1 · answered by antonia w 1 · 0⤊ 0⤋
The fastest way to answer this kind of question is to find the common factor of either x or y as they can be cancel directly
-4x+7y=-10 ---- Equation 1
x-5y=9 ---- Equation 2
As you can see, it is much easier to make the x in equation 2 to become 4x by multiply the whole equation 2 by 4.
You get :
4x-20y=36 ----- Equation 3
Simply solve by Equation 1 + Equation 3
-4x+4x -20y+7y=-10+36
-13y=26
y = 26/-13
y=-2
Substitute y=-2 into Equation 2
x-5y=9
x-(5*-2)=9 Note here that - sign multiply - sign will give you a + sign
x+10=9
x=9-10
x=-1
Answer : x=-1 and y=-2
2007-01-09 07:47:47 · answer #2 · answered by cls22cls 2 · 0⤊ 0⤋
-4x+7y= -10
x-5y=9 multiply by 4
4x-20y=36
-4x+7y= -10 add
-13y=26 divide both sides by -13
y=-2
x-5y=9 substitute y=-2
x-5(-2)=9
x+10=9 subtract 10 from each side
x=-1
(-1, -2)
check
-4(-1)+7(-2)=-10
4-14=-10
-10=-10
2007-01-09 03:10:14 · answer #3 · answered by yupchagee 7 · 0⤊ 0⤋
x = -1 and y = -2
easiest to see if you multiply x-5y = 9 by 4 but let's do it the hard way
- 4x + 7y = - 10 (1)
multiply (1) by 5:
- 20x + 35y = - 50 (2)
x - 5y = 9 (3)
multiply (3) by 7:
7x - 35 y = 63 (4)
add (2) and (4): (to eliminate 35y)
- 13x = 13
x = -1
substitute in (3):
- 1 - 5y = 9
5y = - 10
y = - 2
2007-01-09 02:22:04 · answer #4 · answered by Anonymous · 0⤊ 0⤋
-4x + 7y = -10
x - 5y = 9
Add 4 times the second equation to the first one.
-13y = 26
y = -2
Substitute into the second equation.
x - 5y = 9
x -5(-2) = 0
x + 10 = 9
x = -1
So (x,y) = (-1,-2)
2007-01-09 02:22:05 · answer #5 · answered by Northstar 7 · 0⤊ 0⤋
I got this all worked out on paper, and then my answer was too big to post....BUT I found an example on a website that may help you figure out what step you are missing.
Go to http://regentsprep.org/Regents/Math/syslin/AlgSysAdd.htm
I think you'll find what you need there. Just go through it slowly and calmly.
You can check your answers to this and other problems at another site: http://www.1728.com/unknwn2.htm
It won't show you how to do the problem, it will only give you the solutions.
Hope that helps.
2007-01-09 02:39:09 · answer #6 · answered by quietude61 3 · 0⤊ 0⤋