Solve the system of equations two ways: 3x+y=5 and x-2y=4 A) using substitution B) using elimination

A. solve for 1 variable

let's solve for x in 2nd equation

add 2y to both sides

x=2y+4

sub 2y+4 for x in other equation

3 (2y+4) + y=5

6y+12+y=5

7y+12=5

minu12 both sides

7y=-7

divide 7

y=-1

sub back

x=2y+4

x=2 (-1) + 4

x=-2+4

x=2

(2,-1)

B. eliminate

eliminate y's

multiply first equation by 2 and add to first

6x+2y=10

x-2y=4 +

7x+0y=14

7x=14

divide by 7

x=2

sub back

x-2y=4

2-2y=4

minus 2

-2y=2

divide - 2

y=-1

(2,-1)

(2,-1) is answer