若x=123456789×123456786,Y=123456788×123456787,试比较x,y大小,解:设123456788=a,

2024-12-12 01:18:12
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回答1:

0.345=a 1.345=a+1 2.69=2(a+1)
1.345×0.345×2.69-1.345³-1.345×0.345²
=(a+1)*a*2(a+1)-(a+1)^3-(a+1)*a^2
=2a(a+1)^2-(a+1)^3-a^2(a+1)
=(a+1)[2a(a+1)-(a+1)^2-a^2]
=-(a+1)
= -1.345