SOLUTION: I am trying to solve this equation by using the Elimination by Addition Method: -7x+4y=-1 and 5x-3y=0 Subsitution method: 2x-3y=5 and y=2x-7 Thank you for your help

Algebra ->  Equations -> SOLUTION: I am trying to solve this equation by using the Elimination by Addition Method: -7x+4y=-1 and 5x-3y=0 Subsitution method: 2x-3y=5 and y=2x-7 Thank you for your help      Log On


   

Question 1036601: I am trying to solve this equation by using the Elimination by Addition Method:
-7x+4y=-1 and 5x-3y=0

Subsitution method:
2x-3y=5 and y=2x-7
Thank you for your help
Answer by Cromlix(4381) About Me  (Show Source):
You can put this solution on YOUR website!
Hi there,
-7x + 4y = -1.....(1)
5x - 3y = 0......(2)
Multiply Eq(1) by 3
Multiply Eq(2) by 4
-21x + 12y = -3...(1)
20x - 12y = 0 ...(2)
Add Eq(1) to Eq(2)
-x ........=-3
x ........= 3
Substitute x = 3 into
Eq(1)
-7x + 4y = -1.....(1)
-7(3) + 4y = -1
-21 + 4y = -1
4y = -1 + 21
4y = 20
y = 5
{3,5} Elimination Method.
........
2x - 3y = 5.......(1)
y = 2x - 7 .......(2)
Substitute (2x - 7)for
the y into Eq(1)
2x - 3y = 5.......(1)
2x -3(2x - 7) = 5
multiply out
2x - 6x + 21 = 5
you now have an equation in x
Collect like terms
-4x = 5 - 21
-4x = -16
x = 4
Substitute x = 4 into
Eq(2)
y = 2x - 7 .......(2)
y = 2(4) - 7
y = 8 - 7
y = 1
{4,1) Substitution Method
Hope this helps :-)