how do you solve the following using the subsitution method 5x+3y=-9 and 2x+y = -4 what are the steps to solve

Answer 1

y = - 4 - 2x
5x + 3(-4 - 2x) = - 9
5x - 12 - 6x = - 9
- x = 3
x = - 3

- 6 + y = - 4
y = 2

x = - 3 , y = 2

Answer 2

Dear Connie, S.

5x + 3y = -9
2x + y = -4

y = -2x - 4

5x + 3( -2x - 4 ) = -9
5x + -6x - 12 = -9
- x = 3
x = - 3

Therefore: y = -2( -3) - 4 0r y = 6 - 4
y = 2

Checking the original equations with our solutions for x and y:


5( -3 ) + 3( 2 ) = -9
-15 + 6 = -9
- 9 = - 9

and 2( -3 ) + 2 = - 4
- 6 + 2 = - 4
- 4 = - 4


Sincerely,
[e-mail]
(a.k.a. calvaliear)

Answer 3

5x+3y=-9
2x+y = -4

5x = -9 -3y
x = -9/5 -3y/5
put it in second equation (in place of x)
2( -9/5 -3y/5 ) + y = -4
-18/5 -6y/5 + y = -4
-6y/5 + y = -4 + 18/5
-6y/5 + 5y/5 = -20/5 + 18/5
-y/5 = -2/5
y/5 = 2/5
y = 2
put in first equation (you can also put it in second eq.)
5x + 3(2) = -9
5x + 6 = -9
5x = -9 -6
5x = -15
x = -15/5
x = -3
therefor
x = -3
y = 2
OK I answered first part correctly for the second part which is what are the steps to solve ?
Well first, look number of equations and number of unknowns
If they are equal then can be solved by substitution method
If number of unknowns are more then number of equations then can not be solved (need more information)
If number of equations more then number of unknowns then can be solved easily by any method you know.
Second, just try put the unknown in a side alone
(like you want to find it) then put what you get in another equation.
Finally after you found a value of one of unknowns then put it in equation (first or second it does not matter you well find the same final answer.

Answer 4

5x + 3y = -9.....eqtn 1


2x + y = -4.......eqtn 2

From 2, y = -4 - 2x

Substitute y = -4 - 2x into eqtn 1 to give one equation and one unknown:

5x + 3y = -9, so

5x + 3(-4 - 2x) = -9, so

5x - 12 - 6x = -9, so

-x = 3, so

x = -3, and y = -4 -2*-3 = -4 + 6 = 2.

Hope this helps, Twiggy.

Answer 5

rearrange 2nd eq: y=-2x-4 substitute into first
eq:

5x+3[-2x-4]= -9
5x-6x-12= -9
-x=3 x= -3 y=2

Answer 6

5x+3y=-9
2x+y = -4

5x+3y=-9
3(2x+y = -4)

5x+3y=-9
6x+3y = -12

Subtract now.

5x+3y=-9
-(6x+3y = -12)

-x + 0 = - 9 + 12
- x = 3, x = -3

Now you know x = - 3, so get any equation and plug in x and see what y is.
This one's easier.

5x+3y=-9
5(-3) + 3y = -9
-15 + 3y = -9
3y = 6
y = 2.

(-3,2)

Answer 7

Solve one of the equations in terms of x. Substitute that equation in the other equation for x and solve for y. Then solve for x by substituting your answer for y in the first equation.

Answer 8

5x + 3y = -9
-3(2x + y = -4)
----------------------
5x + 3y = -9
-6x - 3y = 12
----------------------
-x=3
-------------
x= -3

Then plug in x and solve for y :)