用乘法公式计算399^2= =
问题描述:
用乘法公式计算399^2= =
答
(400-1)*(400-1)=160000-800+1=159201
答
=392乘以392=153664
答
399^2
=(400-1)^2
=400^2-2*1*400+1^2
=160000-800+1
=159201