Solve (x + 1 - 7).

y

=

4

Explanation:

First rearrange the two equations so

y

is a function of

x

:

x

+

y

=

8

→

y

=

8

-

x

[

1

]

x

-

2

y

=

-

4

→

y

=

1

2

x

+

2

[

2

]

Because these are straight lines, we only need to put in two values of

x

for each equation and then calculate the corresponding values of

y

.

[

1

]

x

=

-

2

,

x

=

6

y

=

8

-

(

-

2

)

=

10

y

=

8

-

(

6

)

=

2

So we have coordinates

(

-

2

,

10

)

and

(

6

,

2

)

[

2

]

=

-

4

,

x

=

6

y

=

1

2

(

-

4

)

+

2

=

0

y

=

1

2

(

6

)

+

2

=

5

So we have coordinates

(

-

4

,

0

)

and

(

6

,

5

)

We now plot each pair of coordinates and join them with a straight line.