计算 (30 16:35:50)

问题描述:

计算 (30 16:35:50)
①(Xm-yn)(Xm+yn)=
②(-1/2a+1/3)2(1/2a-1/3b)2
③(-2X2+1/2)(-2X2-1/2)

①(Xm-yn)(Xm+yn)=XM²-YN²
②(-1/2a+1/3)2(1/2a-1/3b)2
如果2是乘可以先提出来
③(-2X2+1/2)(-2X2-1/2)
平方差公式(A-B)(A+B)=A²-B²