Show that:
(9p−5q)2+180pq=(9p+5q)2
L.H.S = (9p−5q)2+180pq
=(9p)2−2×9p×5q+(5q)2+180pq
[Using identity (a−b)2=a2–2ab+b2]
=81p2−90pq+25q2+180pq
=81p2+90pq+25q2
=(9p)2+2×9p×5q+(5q)2
=(9p+5q)2 [∵(a+b)2=a2+2ab+b2]
Hence, (9p−5q)2+180pq=(9p+5q)2 Proved