21^3-15^2=
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24 tháng 2 2022
a: =1/8-1/8+2/5=2/5
b: =(-1/15-14/15)+(23/27+31/27)=2-1=1
c: \(=\dfrac{3}{7}\left(\dfrac{22}{21}+\dfrac{5}{21}+\dfrac{15}{21}\right)=\dfrac{3}{7}\cdot2=\dfrac{6}{7}\)
d: \(=\dfrac{-8}{9}\cdot\dfrac{3}{2}+\dfrac{1}{9}\cdot\dfrac{-3}{2}=-\dfrac{3}{2}\)
3 tháng 8 2021
a) Ta có: \(\dfrac{-11}{15}< \dfrac{x}{15}< \dfrac{-8}{15}\)
nên -11<x<-8
hay \(x\in\left\{-10;-9\right\}\)
b) Ta có: \(\dfrac{3}{7}< \dfrac{x}{21}< \dfrac{2}{3}\)
\(\Leftrightarrow\dfrac{9}{21}< \dfrac{x}{21}< \dfrac{14}{21}\)
Suy ra: 9<x<14
hay \(x\in\left\{10;11;12;13\right\}\)
c) Ta có: \(\dfrac{-67}{21}< \dfrac{x}{168}< \dfrac{-3}{8}\)
nên \(\dfrac{-536}{168}< \dfrac{x}{168}< \dfrac{-63}{168}\)
Suy ra: -536<x<-63
hay \(x\in\left\{-535;-534;...;-64\right\}\)
HM
1
AH
Akai Haruma
Giáo viên
13 tháng 8 2023
Lời giải:
$B=\frac{3}{2}-\frac{2}{21}-\frac{7}{12}+\frac{15}{21}-\frac{1}{3}+\frac{5}{4}-\frac{2}{7}-\frac{1}{3}$
$=(\frac{3}{2}+\frac{5}{4})+(\frac{-2}{21}+\frac{15}{21}+\frac{-2}{7})+(\frac{-7}{12}+\frac{-1}{3}+\frac{-1}{3})$
$=\frac{11}{4}+\frac{1}{3}-\frac{5}{4}=\frac{11}{6}$
26 tháng 7 2023
a: \(=\dfrac{3}{5}:\dfrac{7}{5}=\dfrac{3}{5}\cdot\dfrac{5}{7}=\dfrac{3}{7}\)
b: \(=\dfrac{9}{17}\left(\dfrac{8}{5}-\dfrac{3}{5}\right)+\dfrac{8}{17}\)
=9/17+8/17=1
c: =>x-3/10=7/15*1/5=7/75
=>x=7/75+3/10=59/150
28 tháng 9 2023
1.
a) 503 + 120 = 623
b) 1000 - 120 = 880
c) 2 + 18 : 2 = 2 + 9 = 11
d) 21 : 7 - 3 = 3 - 3 = 0
2.
a) x - 3 = 21 => x = 24
b) 15 - x . 3 = 6 => 15 - 3x = 6 => 3x = 15 - 6 = 9 => x = 3
c) x + 21 : 7 = 6 => x + 3 = 6 => x = 3
d) 44 + x : 3 = 50 => x : 3 = 50 - 44 = 6 => x = 18
3.
a) 15 . (21 - 3 . 7) = 15 . (21 - 21) = 15 . 0 = 0
b) (4 : 2 - 2) . 105 = (2 - 2) . 105 = 0 . 105 = 0
c) 376 + 285 + 124 + 715 = 1500
d) 97 + 998 + 9999 + 16 = 11110
e) 252 + 139 - 52 - 39 = 300
4.
a) b - a = 5 - 3 = 2
b) a + b = 3 + 5 = 8
c) 2a + b = 2*3 + 5 = 6 + 5 = 11
d) a . (b + 1) = 3 . (5 + 1) = 3 . 6 = 18
5.
a) 37581 - 9999 = 27582
b) 7345 - 1998 = 5347
c) 485321 - 99999 = 385322
d) 7593 - 1997 = 5596
6.
a) (x - 42) - 110 = 0 => x - 42 = 110 => x = 110 + 42 = 152
b) 2436 : x = 12 => x = 2436 / 12 = 203
c) 74 . (x - 3) = 0 => x - 3 = 0 => x = 3
d) x - 36 : 18 = 2 => x - 2 = 36 => x = 36 + 2 = 38
7.
a) 67 + 135 + 33 = 235
b) 997 + 86 = 1083
c) 37 . 38 + 62 . 37 = 1406
d) 43 . 11 = 473
e) 67 . 99 = 6633
8.
a) 71 - (33 + x) = 26 => 71 - 33 - x = 26 => 38 - x = 26 => x = 38 - 26 = 12
b) 97 - (64 - x) = 44 => 97 - 64 + x = 44 => x = 44 - 97 + 64 => x = 11
c) x - 36 : 18 = 12 => x - 2 = 12 => x = 14
d) 3636 : (12 . x - 91) = 36 => 3636 = 36 * (12 . x - 91) => 3636 = 432 . x - 3276 => 432 . x = 3636 + 3276 => 432 . x = 6912 => x = 6912 / 432 => x = 16
e) ( x : 23 + 45) . 67 = 8911 => (x / 23 + 45) . 67 = 8911 => (x / 23 + 45) = 8911 / 67 => (x / 23 + 45) = 133 => x / 23 = 133 - 45 => x / 23 = 88 => x = 88 . 23 => x = 2024
9.
a) 1 + 2 + 3 + ... + 1998 + 1999 = (1999 . (1999 + 1)) / 2 = 1999 . 2000 / 2 = 1999 . 1000 = 1,999,000
b) Tính tổng tất cả các số tự nhiên có 3 chữ số: Tổng các số từ 100 đến 999 = (100 + 999) / 2 * (999 - 100 + 1) = 1099 / 2 * 900 = 549.5 * 900 = 494550
c) Tính tổng tất cả các số lẻ có 3 chữ số: Các số lẻ từ 101 đến 999 là 101, 103, 105, ..., 999. Số lượng các số này là 450 (900 / 2). Tổng các số này là (101 + 999) / 2 * (450) = 550 * 450 = 247,500
10.
a) 53 . 39 + 47 . 39 - 53 . 21 - 47 . 21 = 2079 + 1833 - 1113 - 987 = 2912
b) 2 . 53 . 12 + 4 . 6 . 87 - 3 . 8 . 40 = 1272 + 1044 - 960 = 1356
c) 47 . 29 - 13 . 29 - 14 . 29 = 1363 - 377 - 406 = 580
d) 1754 : 17 - 74 : 17 + 20 : 17 = 103 - 4 + 1 = 100
e) 26 . 7 - 17 . 9 + 13 . 26 - 17 . 11 = 182 - 153 + 338 - 187 = 180
30 tháng 1 2022
Bài 1:
\(A=\dfrac{-1}{3}+1+\dfrac{1}{3}=1\)
\(B=\dfrac{2}{15}+\dfrac{5}{9}-\dfrac{6}{9}=\dfrac{2}{15}-\dfrac{1}{9}=\dfrac{18-15}{135}=\dfrac{3}{135}=\dfrac{1}{45}\)
\(C=\dfrac{-1}{5}+\dfrac{1}{4}-\dfrac{3}{4}=\dfrac{-1}{5}-\dfrac{1}{2}=\dfrac{-7}{10}\)
Bài 2:
a: \(=\dfrac{1}{5}+\dfrac{1}{2}+\dfrac{2}{5}-\dfrac{3}{5}+\dfrac{2}{21}-\dfrac{10}{21}+\dfrac{3}{20}\)
\(=\left(\dfrac{1}{5}+\dfrac{2}{5}-\dfrac{3}{5}\right)+\left(\dfrac{2}{21}-\dfrac{10}{21}\right)+\left(\dfrac{1}{2}+\dfrac{3}{20}\right)\)
\(=\dfrac{-8}{21}+\dfrac{13}{20}=\dfrac{113}{420}\)
b: \(B=\dfrac{21}{23}-\dfrac{21}{23}+\dfrac{125}{93}-\dfrac{125}{143}=\dfrac{6250}{13299}\)
30 tháng 1 2022
Bài 3:
\(\dfrac{7}{3}-\dfrac{1}{2}-\left(-\dfrac{3}{70}\right)=\dfrac{7}{3}-\dfrac{1}{2}+\dfrac{3}{70}=\dfrac{490}{210}-\dfrac{105}{210}+\dfrac{9}{210}=\dfrac{394}{210}=\dfrac{197}{105}\)
\(\dfrac{5}{12}-\dfrac{3}{-16}+\dfrac{3}{4}=\dfrac{5}{12}+\dfrac{3}{16}+\dfrac{3}{4}=\dfrac{20}{48}+\dfrac{9}{48}+\dfrac{36}{48}=\dfrac{65}{48}\)
Bài 4:
\(\dfrac{3}{4}-x=1\)
\(\Rightarrow-x=1-\dfrac{3}{4}\)
\(\Rightarrow x=-\dfrac{1}{4}\)
Vậy: \(x=-\dfrac{1}{4}\)
\(x+4=\dfrac{1}{5}\)
\(\Rightarrow x=\dfrac{1}{5}-4\)
\(\Rightarrow x=-\dfrac{19}{5}\)
Vậy: \(x=-\dfrac{19}{5}\)
\(x-\dfrac{1}{5}=2\)
\(\Rightarrow x=2+\dfrac{1}{5}\)
\(\Rightarrow x=\dfrac{11}{5}\)
Vậy: \(x=\dfrac{11}{5}\)
\(x+\dfrac{5}{3}=\dfrac{1}{81}\)
\(\Rightarrow x=\dfrac{1}{81}-\dfrac{5}{3}\)
\(\Rightarrow x=-\dfrac{134}{81}\)
Vậy: \(x=-\dfrac{134}{81}\)
LM
Lê Minh Vũ
CTVHS
15 tháng 6 2023
3 x 15 + 21 x 15 + 85 x 5
= 45 + 315 + 425
= 785
15 - 30 + 40
= 25
21 + 19 - 50 + 10
= 0
\(\dfrac{1}{5}-\dfrac{1}{4}+2\)
\(=-\dfrac{1}{20}+2\)
\(=\dfrac{39}{20}\)
\(\left(\dfrac{1}{4}+\dfrac{1}{6}\right)\times\left(\dfrac{1}{2}-\dfrac{1}{4}\right)\)
\(=\dfrac{5}{12}\times\dfrac{1}{4}\)
\(=\dfrac{5}{12}\times\dfrac{3}{12}\)
\(=\dfrac{5}{48}\)
\(\dfrac{1}{10}+\dfrac{1}{5}-\dfrac{3}{4}\)
\(=-\dfrac{9}{20}\)
BD
15 tháng 6 2023
\(3\times15+21\times15+85\times5\\ =15\times\left(3+21\right)+425\\ =15\times24+425\\ =360+425\\ =785\)
\(15-30+40\\ =\left(15+40\right)-30\\ =55-30\\ =25\)
\(21+19-50+10\\ =\left(21+19\right)-\left(50-10\right)\\ =40-40\\ =0\)
\(\dfrac{1}{5}-\dfrac{1}{4}+2\)
\(=\dfrac{4}{20}-\dfrac{5}{20}+\dfrac{40}{20}\)
\(=\dfrac{\left(4+40\right)}{20}-\dfrac{5}{20}\)
\(=\dfrac{44}{20}-\dfrac{5}{20}\)
\(=\dfrac{39}{20}\)
\(\left(\dfrac{1}{4}+\dfrac{1}{6}\right)\times\left(\dfrac{1}{2}-\dfrac{1}{4}\right)\)
\(=\dfrac{5}{12}\times\dfrac{1}{4}\)
\(=\dfrac{5}{48}\)
\(\dfrac{1}{10}+\dfrac{1}{5}-\dfrac{3}{4}\)
\(=\dfrac{2}{20}+\dfrac{4}{20}-\dfrac{15}{20}\)
\(=\dfrac{6}{20}-\dfrac{15}{20}\)
\(=-\dfrac{9}{20}\)
Trả lời:
213 - 152
= 9261 - 225
= 9036
Trả lời:
213 - 152
= 9036