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46.37 + 93.46 + 54.61 + 69.54
= 46.(37+93) + 54.(61+69)
= 46. 130 + 54.130
= 130.(46+54)
= 130.100 = 13 000
46 . 37 + 93 . 46 + 54 . 61 + 69 . 54
= 46 . (37+ 93) + 54 . (61 + 69)
= 46 . 130 + 54 . 130
= (46 + 54) . 130
= 100 . 130
= 13000
Hình vẽ :
Giải : a) Vì M nằm giữa A và B(AM < AB) nên AM + MB = AB
=> BM = AB - AM = 12 - 6 = 6 (cm)
b) N là trung điểm của BM => BN = NM = BM/2 = 6/2 = 3 (cm)
Vì M nằm giữa A và N nên AM + NM = AN
=> AN = 6 + 3 = 9 (cm)
6. Ta có : 3n + 13 = 3(n + 2) + 4
Do n + 2 \(⋮\)n + 2 => 3(n + 2) \(⋮\)n + 2
Để 3n + 13 \(⋮\)n + 2 thì 4 \(⋮\)n + 2 => n + 2 \(\in\)Ư(4) = {1; 2; 4}
Lập bảng :
| n + 2 | 1 | 2 | 4 |
| n | -1 | 0 | 2 |
Vì n là số tự nhiên => n = 0 hoặc 2 thì 3n + 13 \(⋮\)n + 2
31: (-29)+8-9
\(=\left(-29\right)+\left(8-9\right)\)
\(=-29-1=-30\)
32: \(\left(-14\right)-6-10\)
\(=\left(-14-6\right)-10\)
=-20-10
=-30
33: \(\left(-42\right)+10+2\)
\(=\left(-42\right)+\left(10+2\right)\)
=-42+12
=-30
34: \(\left(-45\right)+25-20\)
\(=\left(-45\right)+\left(25-20\right)\)
=-45+5
=-40
35: \(\left(-60\right)+17+3\)
\(=\left(-60\right)+\left(17+3\right)\)
=-60+20
=-40
36: \(\left(-48\right)+18-10\)
\(=\left(-48+18\right)-10\)
=-30-10
=-40
câu d)
\(\dfrac{6}{5}+\left(3+\dfrac{-1}{5}\right)\\ =\dfrac{6}{5}+3+\dfrac{-1}{5}\\ =1+3=4\)
câu e)
\(-\dfrac{3}{5}+\left(-\dfrac{2}{5}+2\right)\\ =\dfrac{-3}{5}+\dfrac{-2}{5}+2\\ =-1+2=1\)
câu f)
\(\dfrac{8}{3}-\left(-\dfrac{4}{3}+3\right)\\ =\dfrac{8}{3}+\dfrac{4}{3}-3\\ =4-3=1\)
Lời giải:
g.
$=\frac{-5}{11}+\frac{-6}{11}+1=(\frac{-5}{11}+\frac{-6}{11})+1$
$=\frac{-11}{11}+1=(-1)+1=0$
h.
$=\frac{-17}{13}+\frac{4}{13}+\frac{25}{101}$
$=\frac{-13}{13}+\frac{25}{101}=(-1)+\frac{25}{101}=-(1-\frac{25}{101})$
$=\frac{-76}{101}$
i.
$=\frac{6}{7}+\frac{1}{8}-\frac{3}{16}.4=\frac{6}{7}+\frac{1}{8}-\frac{3}{4}$
$=\frac{6}{7}+\frac{1}{8}-\frac{6}{8}=\frac{6}{7}+\frac{-5}{8}$
$=\frac{13}{56}$
CÂU A)
\(\dfrac{5}{3}+\left(7+\dfrac{-5}{3}\right)\\ =\dfrac{5}{3}+7+\dfrac{-5}{3}=7\)
CÂI B)
\(-\dfrac{7}{31}+\left(\dfrac{24}{17}+\dfrac{7}{31}\right)\\ =-\dfrac{7}{31}+\dfrac{24}{17}+\dfrac{7}{31}=\dfrac{24}{17}\)
CÂU C)
\(\dfrac{3}{7}+\left(-\dfrac{1}{5}+\dfrac{-3}{7}\right)\\ =\dfrac{3}{7}-\dfrac{1}{5}-\dfrac{3}{7}=-\dfrac{1}{5}\)
k.
$=\frac{-5}{7}(\frac{2}{11}+\frac{9}{11})+\frac{12}{7}$
$=\frac{-5}{7}.\frac{11}{11}+\frac{12}{7}$
$=\frac{-5}{7}+\frac{12}{7}=\frac{7}{7}=1$
l.
$=(\frac{1}{5}+\frac{4}{5})+(\frac{-2}{9}+\frac{-7}{9})+\frac{16}{17}$
$=\frac{5}{5}+\frac{-9}{9}+\frac{16}{17}$
$=1+(-1)+\frac{16}{17}=\frac{16}{17}$
a.
$=(\frac{-17}{13}+\frac{4}{13})+(\frac{11}{31}+\frac{20}{31})+\frac{2}{135}$
$=\frac{-13}{13}+\frac{31}{31}+\frac{2}{135}=(-1)+1+\frac{2}{135}=\frac{2}{135}$
b.
$=(\frac{3}{17}+\frac{20}{-17})+(\frac{4}{18}+\frac{-2}{9})+(\frac{5}{8}+\frac{21}{56})$
$=(\frac{3}{17}+\frac{-20}{17})+(\frac{2}{9}+\frac{-2}{9})+(\frac{5}{8}+\frac{3}{8})$
$=\frac{-17}{17}+\frac{0}{9}+\frac{8}{8}$
$=(-1)+0+1=0$
c.
$=\frac{-5}{12}+\frac{6}{11}+\frac{7}{17}+\frac{5}{11}+\frac{5}{12}$
$=(\frac{-5}{12}+\frac{5}{12})+(\frac{6}{11}+\frac{5}{11})+\frac{7}{17}$
$=\frac{0}{12}+\frac{11}{11}+\frac{7}{17}$
$=0+1+\frac{7}{17}=\frac{24}{17}$
d.
$=\frac{9}{16}+\frac{-8}{27}+1+\frac{7}{16}+\frac{-19}{27}$
$=(\frac{9}{16}+\frac{7}{16})+1+(\frac{-8}{27}+\frac{-19}{27})$
$=\frac{16}{16}+1+\frac{-27}{27}$
$=1+1+(-1)=1$
46.37+93.46+54.61+69.54
=46.(93+37)+54.(61+69)
=46.130+54.130
=130.(46+54)
=130.100
=13000
46 . 37 + 93 . 46 + 54 . 61 + 69 . 54
= 46 . ( 37 + 93 ) + 54 . ( 61 + 69 )
= 46 . 130 + 54 . 130
= 130 . ( 46 + 54 )
= 130 . 100
= 13000