Question

Add: p (p − q), q (q _­­­− r) and r (r ­− p)

Answer 1

First expression = p (p − q) = p² − pq

Second expression = q (q _­­­− r) = q² − qr

Third expression = r (r ­− p) = r² − pr

Adding the three expressions, we obtain.

   p² − pq
+             q² − qr
+                           r² − pq
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p² − pq + q² − qr + r² − pq

Therefore, the sum of the given expressions is p² + q² + r² − pq − qr − rp.