Question

Solve each system of equations using substitution. Show all work.

1) y = 2x - 5
4x - y = 7

2) 2x - 3y = 12
x = 4y + 1

3) y = 5 - x
x - 4y = 10

Answer 1

1.
y=2x-5
sub that for y
4x-(2x-5)=7
distribute
4x-2x+5=7
2x+5=7
2x=2
x=1
sub back
y=2x-5
y=2(1)-5
y=2-5
y=-3

(1,-3)




2. x=4y+1
sub that for x
2(4y+1)-3y=12
8y+2-3y=12
5y+2=12
5y=10
y=2
sub back
x=4y+1
x=4(2)+1
x=8+1
x=9

(9,2)



3. y=5-x
sub that for y
x-4(5-x)=10
x-20+4x=10
5x-20=10
5x=30
x=6
sub back
y=5-x
y=5-6
y=-1
(6,-1)



soluitons

1. (1.-3)
2. (9,2)
3. (6,-1)