Question

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

Answer 1

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