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1990.1990-1992.1998=-19916
...............................=100
...............................=1
k mink nha
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)
a)
1990.1990 -1992.1998 = (1995-5)^2 -(1995+3)(1995-3) = -10.1995 +25 +9 = -(19950-34) = -19916
b)
ta có
tu = 124 .237 +152 = 122.137 + 474 +152= 122. 137 + 626
mau = ( 870 + (237-2).122= 870 +122.237 - 244 =122.237 + 626
=> phân thức đã cho = tử/mẫu = 1
a/ \(=1990.1990-\left(1990+2\right).\left(1990-2\right)=1990.1990-\left(1990.1990-4\right)=4\)
b/ \(=\frac{2.687.57+687.86}{26.13+74.\left(13+1\right)}=\frac{687\left(2.57+86\right)}{26.13+74.13+74}=\frac{687.\left(114+86\right)}{13\left(26+74\right)+74}=\)
\(=\frac{687.200}{13.100+74}=\frac{687.200}{1374}=\frac{687.200}{687.2}=\frac{200}{2}=100\)
c/ \(=\frac{214.237+152}{870+\left(237-2\right).\left(124-2\right)}=\frac{124.237+152}{870+124.237-2.237-2.124+4}=\)
\(=\frac{124.237+152}{124.237+870+4-2.237-2.124}=\frac{124.237+152}{124.237+152}=1\)
a, 1990 . 1990 - 1992 . 1988
= 3960100 - 3960096
= 4 .
b, ( 1374 . 57 + 687 . 86 ) : ( 26 . 13 + 74 . 14 )
= ( 78318 + 59082 ) : ( 338 + 1036 )
= 137400 : 1374
= 100 .
c, \(\frac{37.13-13}{24 +37.12}\)
\(=\frac{37.\left(12+1\right)-13}{24+37.12}\)
\(=\frac{37.12+37-13}{24+37.12}\)
\(=\frac{37.12+24}{24+37.12}\)
\(=1\)
a)\(1990.1990-1992.1988\)
\(=1990.1990-\left(1990+2\right).\left(1990-2\right)\)
\(=1990.1990-\left(1990^2-4\right)\)
\(=4\)
P/s :Bài này có áp dụng hằng đẳng thức , nên ko bt có phù với với lớp 6 ko :))
\(1990.1990-1992.1988\) \(\left(124.237+152\right):\left(870+235.122\right)\)
\(=3960100-3960096\) \(=\left(29388+152\right):\left(870+28670\right)\)
\(=4\) \(=29540:29540\)
\(=1\)
a) Xét 1992.1998 = (1995 - 3).(1995 + 3) = 1995.(1995 + 3) - 3.(1995 + 3) = 19952 + 1995.3 - 3.1995 - 32 = 19952 - 9
Vậy 19952 - 1992.1998 = 19952 - (19952 - 9) = 9
bang 9