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\(\dfrac{423134.846267-423133}{846267.423133+423134}.\)
\(=\dfrac{\left(423133+1\right).846267-423133}{846267.423133+423134}.\)
\(=\dfrac{423133.846267+\left(846267-423133\right)}{846267.423133+423134}.\)
\(=\dfrac{423133.846267+423134}{846267.423133+423134}=1.\)
Vậy..........
\(\dfrac{423134\cdot846267-423133}{846267\cdot423133+423134}\)
\(=\dfrac{(423133+1)\cdot846267-423133}{846267\cdot423133+423134}\)
\(=\dfrac{423133\cdot846267+846267-423133}{846267\cdot423133+423134}\)
\(=\dfrac{423133\cdot846267+423134}{864267\cdot423133+423134}=1\)
\(=\frac{\left(423133+1\right).846267-423133}{846267.423133+423134}=\frac{846267.423133+846267-423133}{846267.423133+423134}=\)
\(=\frac{846267.423133+423134}{846267.423133+423134}=1\)
a)1990*1990-1992*1988=1990*(1988+2)-(1990+2)*1988=1990*1988+2*1990-1990*1988-2*1988=(1990*1988-1990*1988)+(2*1990-2*1988)=0+2*(1990-1988)=2*2=4
b)(1374*57+687*86)/(26*13+74*14)=(687*2*57+687*86)/(26*13+74+74*13)=(687*114+687*86)/(100*13+74)
=(687*200)/1374=137400/1374=100
c)(124*237+152)/(870+235*122)=\(\frac{\left(122+2\right)\cdot237+152}{870+\left(237-2\right)\cdot122}=\frac{122\cdot237+2\cdot237+152}{870-2\cdot122+237\cdot122}=\frac{122\cdot237+626}{626+237\cdot122}=1\)
d)\(\frac{423134\cdot846267-423133}{846267\cdot423133+423134}=\frac{\left(423133+1\right)\cdot846267-423133}{846267\cdot423133+423134}\)
\(=\frac{423133\cdot846267+846267-423133}{846267\cdot423133+423134}=\frac{423133\cdot846267+423134}{846267\cdot423133+423134}=1\)
(mỏi hết cả mắt)
\(\frac{423134.846267-423133}{846267.423133+423134}\)
Xét tử số : 423134.846267-423133
= (423133+1).846267-423133
= 423133.846267+846267-423133
=423133.846267+ 423134
Ta có : \(\frac{423133.846267+423134}{846267.423133+423134}\)=1
\(\frac{423134.846267-423133}{846267.423133+423134}=\frac{\left(423134+1\right).846267-423133}{846267.423133+423134}\)
\(\frac{423133.846267+846267-423133}{846267.423133-423134}=\frac{423133.846267-423134}{864267.423133-423134}=1\)