19+79
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![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
-79-79.99
=-79+(-79).99
=-79.100=-7900
19-42(-19)+38.5
=19.1+42.19+19.10
=19(1+42+10)
=19.53
=1007
![](https://rs.olm.vn/images/avt/0.png?1311)
b) -123.47 + 47.23 = -47(123 - 23) = -47.100 = -4700
![](https://rs.olm.vn/images/avt/0.png?1311)
a) Ta có:
\(A=\dfrac{-68}{123}\cdot\dfrac{-23}{79}=\dfrac{68}{123}\cdot\dfrac{23}{79}\)
\(B=\dfrac{-14}{79}\cdot\dfrac{-68}{7}\cdot\dfrac{-46}{123}=-\left(\dfrac{14}{79}\cdot\dfrac{68}{7}\cdot\dfrac{46}{123}\right)\)
\(C=\dfrac{-4}{19}\cdot\dfrac{-3}{19}\cdot...\cdot\dfrac{0}{19}\cdot...\cdot\dfrac{3}{19}\cdot\dfrac{4}{19}=0\)
Suy ra A là số hữu tỉ dương, B là số hữu tỉ âm và C là 0.
Vậy A > C > B.
b) Ta có:
\(\dfrac{B}{A}=\dfrac{-\left(\dfrac{14}{79}\cdot\dfrac{68}{7}\cdot\dfrac{46}{123}\right)}{\dfrac{68}{123}\cdot\dfrac{23}{79}}=-\dfrac{14}{79}\cdot\dfrac{68}{7}\cdot\dfrac{46}{123}\cdot\dfrac{123}{68}\cdot\dfrac{79}{23}\)
\(\dfrac{B}{A}=-\dfrac{14\cdot68\cdot46\cdot123\cdot79}{79\cdot7\cdot123\cdot68\cdot23}=-\left(2\cdot2\right)=-4\)
Vậy B : A = -4
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{67}{43}+\frac{106}{79}+\frac{52}{79}+\frac{19}{43}\)
\(=\left(\frac{67}{43}+\frac{19}{43}\right)+\left(\frac{106}{79}+\frac{52}{79}\right)\)
\(=2+2\)
\(=4\)
\(Ta\) \(có\)
\(\frac{67}{43}+\frac{106}{79}+\frac{52}{79}+\frac{19}{43}\)
\(=\left(\frac{67}{43}+\frac{19}{43}\right)+\left(\frac{106}{79}+\frac{52}{79}\right)\)
\(=\frac{86}{43}+\frac{158}{79}\)
\(=\frac{6794}{3397}+\frac{6794}{3397}\)
\(=\frac{13588}{10094}=\frac{6794}{5047}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Bỏ dấu ngoặc rồi tính:
a)(2015-79+19)-(-79+19)
b)-(515-80+91)-(2020+80-91)
Giải:
a,Ta có:(2015-79+19)-(-79+19)=2015-79+19+79-19
=2015-79+79+19-19
=2015+0+0=2015
b,-(515-80+91)-(2020+80-91)=-515+80-91-2020-80+91
=-515-2020+80-80-91+91
=-2535+0+0=-2535
a) (2015-79+19)-(-79+19)
= 2015 - 79 +19 + 79 -19
= 2015 + (79- 79) + (19 -19)
= 2015
b) - (515 - 80 +91) -(2020 +80-91)
= -515 + 80 - 91 - 2020 -80 +91
= -515 -2020 +( 80 -80) + (91 -91)
= -2535
![](https://rs.olm.vn/images/avt/0.png?1311)
Câu 1:
(136-63+79)-(136+79)
= 136-63+79-136-79
= 136 + (-63) + 79 + (-136) + (-79)
= 136 + (-136) + 79 + (-79) +(-63)
= 0 + 0 + (-63)
= -63
Câu 2:
-(41+19+22)-(19+22)
= -41 - 19 - 22 - 19 -22
= -41 + (-19) + (-22) + (-19) + (-22)
= (-19) + (-19) + (-22) + (-22) + (-41)
= (-38) + (-44) + (-41)
= (-123)
Giáng sinh vui vẻ nha!
19+79=98
bang 98