A
d
d
x
2
-
y
2
-
1
,
y
2
-
1
-
x
2
,
1
-
x
2
-
y
2
a
n
d
f
i
n
d
t
h
e
d
e
g
r
e
e
o
f
t
h
e
e
x
p
r
e
s
s
i
o
n
.
Matching exercise
Match the items on the right to the items on the left.
Check
OK
STEP1
STEP2
STEP3
STEP4
STEP5
