2)( -)( +) + (-)(+) = 13
()^2 - ()^2 + ()^2 - ()^2 = 13
- + - = 13
= 13
13() = 13 * 36
= 36
3) = 20
() - 2ab = 20
- 2ab = 20
36 - 2ab = 20
2ab = 16
ab = 8
2)(
-
)(
+
) + (
-
)(
+
) = 13
(
)^2 - (
)^2 + (
)^2 - (
)^2 = 13
13(
) = 13 * 36
3)
= 20
(
) - 2ab = 20
36 - 2ab = 20
2ab = 16
ab = 8