a ) ( - 31 ) . 72 – (-31 ). 70 – 31 . 2
b ) 55 . (- 23 ) – 45. 23 + 34 .( -13 ) - 66.13
c ) e) 25. ( 32 + 47 ) – 32 . ( 25 + 47 )
giúp
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31x72 - 31x70 - 31 x 2 - 31
=31x(72 -70 -2 -1)
=31 x (-1)
= -31
những câu sau thì lam tương tự nha bạn ^_^
a: =25x100-150=2500-150=2350
c: \(=520:\left\{515\cdot25\right\}\)
=104/2575
a. ( - 57 ) . ( 67 - 34 ) - 67 . (34 -57 )
= - 57 . 67 - ( - 57 ) . 34 - 67 . 34 - 67 . 57
= 57 . ( 67 - 67 ) + 34 . ( 67 - 57 )
= 57 . 0 + 34 . 10
= 0 + 340
= 340
a. \(\dfrac{10}{21}>1\)
\(\dfrac{9}{23}< 1\)
\(\Rightarrow\dfrac{10}{21}>\dfrac{9}{23}\)
b. \(\dfrac{32}{33}>\dfrac{31}{33}>\dfrac{31}{34}\Rightarrow\dfrac{32}{33}>\dfrac{31}{34}\)
c. \(\dfrac{44}{47}< \dfrac{45}{47}< \dfrac{45}{46}\Rightarrow\dfrac{44}{47}< \dfrac{45}{46}\)
\(d.\dfrac{70}{117}< \dfrac{70}{115}=\dfrac{14}{23}\Rightarrow\dfrac{70}{117}< \dfrac{14}{23}< \dfrac{15}{23}\)
\(\Rightarrow\dfrac{70}{117}< \dfrac{15}{23}\)
a) \(31\cdot72+\left(-31\right)\cdot70-2\cdot70\)
\(=31\cdot72-31\cdot70-2\cdot70\)
\(=31\cdot\left(72-70\right)-2\cdot70\)
\(=31\cdot2-2\cdot70\)
\(=2\cdot\left(31-70\right)\)
\(=2\cdot-39\)
\(=-78\)
b) \(25\cdot\left(32+17\right)-32\cdot\left(25+47\right)\)
\(=25\cdot32+25\cdot17-32\cdot25-32\cdot47\)
\(=25\cdot\left(32-32+17\right)-32\cdot47\)
\(=25\cdot17-32\cdot47\)
\(=425-1504\)
\(=-1079\)
1) $(-35)\cdot18+28\cdot35$
$=35\cdot(-18)+28\cdot35$
$=35\cdot(-18+28)$
$=35\cdot10$
$=350$
2) $53\cdot29-47\cdot(-29)$
$=53\cdot29-47\cdot(-1)\cdot29$
$=53\cdot29+47\cdot29$
$=29\cdot(53+47)$
$=29\cdot100$
$=2900$
3) $125\cdot(-24)+24\cdot225$
$=(-125)\cdot24+24\cdot225$
$=24\cdot(-125+225)$
$=24\cdot100$
$=2400$
4) $26\cdot(-121)-121\cdot(-36)$
$=-121\cdot[26+(-36)]$
$=-121\cdot(26-36)$
$=-121\cdot(-10)$
$=121\cdot10$
$=1210$
5) $65\cdot(-25)+25\cdot(-23)$
$=-65\cdot25+25\cdot(-23)$
$=25\cdot(-65-23)$
$=25\cdot(-88)$
$=-2200$
6) $237\cdot(-26)+26\cdot137$
$=-237\cdot26+26\cdot137$
$=26\cdot(-237+137)$
$=26\cdot(-100)$
$=-2600$
7) $30\cdot(-125)+25\cdot30$
$=30\cdot(-125+25)$
$=30\cdot(-100)$
$=-3000$
8) $(-37)\cdot69+(-31)\cdot37$
$=37\cdot(-69)+37\cdot(-31)$
$=37\cdot(-69-31)$
$=37\cdot(-100)$
$=-3700$
9) $31\cdot72-31\cdot70-31\cdot2$
$=31\cdot(72-70-2)$
$=31\cdot(2-2)$
$=31\cdot0$
$=0$
10) $(-12)\cdot47+(-12)\cdot52+(-12)$
$=-12\cdot(47+52+1)$
$=-12\cdot100$
$=-1200$
$\text{#}Toru$
1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20+21+22+23+24+25+26+27+28+29+30+31+32+33+34+35+36+37+38+39+40+41+42+43+44+45+46+47+48+49+50=1275
a ) ( - 31 ) . 72 – (-31 ). 70 – 31 . 2
= ( - 31 ) . 72 – (-31 ). 70 +(-31) . 2
= (-31) . ( 72-70 +2)
= -31 . 4
= -124
b ) 55 . (- 23 ) – 45. 23 + 34 .( -13 ) - 66.13
= 55 . (- 23 ) + 45. (-23)+ 34 .( -13 ) + 66.(-13)
= -23. ( 55+45) + ( -13) . (34+66)
= -23 . 100 + (-13) . 100
= -2300 + (-1300)
= -3600
c ) e) 25. ( 32 + 47 ) – 32 . ( 25 + 47 )
= 25 . 79 - 32 . 72
= 1975 - 2304
= -329
( mik chưa nghĩ ra cách câu c nên mik tính thường nhá :D)