Simultaneous equations

1. {x=4y+7-----------1
{x=7-8y-----------2

1x2:
2x=8y+14--------3

3+2:
3x=21
x=7

Sub.x=7into 1

7=4y+7
y=0


2. {x=3y -------1
{x-2y=5=0--------2

Because 5 is not eaqul to 0
so I cannot slove for you!

3. {y=5x+2=6x+3
{y=5x+2----------1
{5x+2=6x+3------2

After rearrang 2
-x=1
x=-1
Sub.x=-1 into 1
y=-5+2
y=-3

4.Given th e equation a-2b-5=0,express a in terms of b.
Find the solution of the folloeing simultaneous equation.

a-2b-5=0
a=2b+5

because there is only one eqution
so I cannot slove for you.



5.{a-2b-5=0-------1
{3a+b+6=0------2

2x2:
6a-2b+12=0-----3
3+1:
7a+7=0
a=-1

Sub.a=-1 into 1

-1-2b-5=0
-2=6
b=-3

1)
x=4y+7 ．．．．(1)
x=-8y+7．．．．(2)
(1)-(2)
0=12y
∴y=0

2)
x=3y．．．．(1)
x-2y=5．．．(2)
sub(1)into(2)
3y-2y=5
∴y=5

4)
a-2b-5=0．．．．(1)
3a+b+6=0．．．．(2)
a=2b+5．．．．(3)
sub(3)into(2)
3(2b+5)+b+6=0
6b 15 b 6=0
7b=-21
b=-3

1.
x=4y+7 -- (1)
x=7-8y -- (2)
Sub (1) into (2),
4y+7=7-8y
12y=0
y=0
Sub y=0 into (1),
x=4(0)+7
x=7

2.
x=3y -- (3)
x-2y=5=0 -- (4) (I think the he first = should be -)
Sub(3) into (4),
3y-2y-5=0
y=5
Sub y=5 into (3),
x=15

3.
y=5x+2=6x+3
Make it become two equation:
y=5x+2 -- (5)
5x+2=6x+3 -- (6)
From (6),
x=-1
Sub x=-1 into (5),
y=5(-1)+2
y=-3

4.
a-2b-5=0
a=2b+5 -- (7)

a-2b-5=0
3a+b+6=0 -- into (8)
Sub (7) into (8),
3(2b+5)+b+6=0
6b+15+b+6=0
7b=-21
b=-3
Sub b=-3 into (7),
3a+(-3)+6=0
3a=-3
a=-1


Hope it can help you!