应用平方差公式a²-b²=(a-b)(a+b)∴p²（p+q）²-q²（p-q）²=[p(p+q)-q(p-q)]×[p(p+q)+q(p-q)]=(p²+pq-pq+q²)(p²+pq+pq-q²)=(p²+q²)(p²+2pq-q²...