（5*5-1）/1=24,5乘以5等于25,25减1等于24，24除以1等于24
1/5=0.25-0.2=4.84.8*5=24
（5+1）x(5-1) = 6x4 = 24 5 x 5 - 1x1 = 25 - 1 = 24 5 x 5 - 1/1 = 25 - 1 = 24
（5+1）x(5-1)=6x4=24
