用乘法公式计算399^2= =

问题描述:

用乘法公式计算399^2= =

(400-1)*(400-1)=160000-800+1=159201

=392乘以392=153664

399^2
=(400-1)^2
=400^2-2*1*400+1^2
=160000-800+1
=159201