sekaligus cara kerja

2p-3q=4 [kalikan 2]
7p+2q=39 [kalikan 3]

4p - 6q = 8
21p+ 6q =117
---------------- +
25p = 125
p = 125/25
p = 5

subtitus=
2(5) -3q = 4
10 - 3q = 4
-3q = 4-10
-3q = -6
q = -6/-3
q = 2

jadi p^2 + q^2 = (5)^2 + (2)^2 = 25 + 4 = 29