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VT
2
29 tháng 10 2016
a ) 13/20
B)
C..........................................................
minh dang tính
8 tháng 2 2021
Bài 5:
a) Ta có: \(x⋮5\)
\(\Leftrightarrow x\in B\left(5\right)\)
\(\Leftrightarrow x\in\left\{....;-15;-10;-5;0;5;10;15;...\right\}\)
mà -12<x<12
nên \(x\in\left\{-10;-5;0;5;10\right\}\)
Vậy: \(x\in\left\{-10;-5;0;5;10\right\}\)
b) Ta có: \(36⋮x\)
\(\Leftrightarrow x\inƯ\left(36\right)\)
\(\Leftrightarrow x\in\left\{-36;-18;-12;-9;-6;-4;-3;-2;-1;1;2;3;4;6;9;12;18;36\right\}\)
mà x<0
nên \(x\in\left\{-36;-18;-12;-9;-6;-4;-3;-2;-1\right\}\)
Vậy: \(x\in\left\{-36;-18;-12;-9;-6;-4;-3;-2;-1\right\}\)
Bài 6:
a) Ta có: \(-24\cdot x=72\)
\(\Leftrightarrow x=72:\left(-24\right)\)
\(\Leftrightarrow x=-72:24=-3\)
Vậy: x=3
b) Ta có: \(-5\cdot\left|x\right|=-30\)
\(\Leftrightarrow\left|x\right|=6\)
hay \(x\in\left\{6;-6\right\}\)
Vậy: \(x\in\left\{6;-6\right\}\)
c) Ta có: \(12\cdot x=\left(-36\right)\)
\(\Leftrightarrow x=-36:12\)
\(\Leftrightarrow x=-3\)
Vậy: x=-3
d) Ta có: \(-8\cdot\left|x\right|=-32\)
\(\Leftrightarrow\left|x\right|=4\)
hay \(x\in\left\{4;-4\right\}\)
Vậy: \(x\in\left\{4;-4\right\}\)
26 tháng 10 2023
2:
a: 3x-15=30
=>3x=45
=>x=45/3=15
b: \(5x+5^2=2^4\cdot5\)
=>\(5x+25=16\cdot5=80\)
=>5x=55
=>x=11
c: \(2+x:5=6\)
=>x:5=4
=>x=4*5=20
d: \(3^x-1=26\)
=>\(3^x=26+1=27\)
=>x=3
5:
a: \(A=1+3+3^2+...+3^{101}\)
\(=\left(1+3+3^2\right)+3^3\left(1+3+3^2\right)+...+3^{99}\left(1+3+3^2\right)\)
\(=13\left(1+3^3+...+3^{99}\right)⋮13\)
b: n+4 chia hết cho n+1
=>\(n+1+3⋮n+1\)
=>\(3⋮n+1\)
=>\(n+1\in\left\{1;-1;3;-3\right\}\)
=>\(n\in\left\{0;-2;2;-4\right\}\)
mà n là số tự nhiên
nên \(n\in\left\{0;2\right\}\)
AH
Akai Haruma
Giáo viên
2 tháng 12 2023
Lời giải:
$\overline{ab9}+\overline{ab}=174$
$\overline{ab}.10+9+\overline{ab}=174$
$\overline{ab}(10+1)+9=174$
$\overline{ab}.11+9=174$
$\overline{ab}=(174-9):11=15$
$\Rightarrow a=1; b=5$
$\Rightarrow a+b=1+5=6$
1 tháng 1 2022
e: \(=\dfrac{-3}{4}+\dfrac{5}{7}=\dfrac{-21+20}{28}=\dfrac{-1}{28}\)
1 tháng 1 2022
a ) \(\dfrac{6}{13}\) + \(\dfrac{-14}{39}\)
= \(\dfrac{6.3}{13.3}\) + \(\dfrac{-14}{39}\)
= \(\dfrac{18}{39}\) - \(\dfrac{14}{39}\)
= \(\dfrac{4}{39}\)
{ các ý còn lại tương tự }
DT
0
XA
3
18 tháng 8 2021
\(d,\dfrac{5}{7}+\dfrac{9}{23}+-\dfrac{12}{7}+\dfrac{14}{23}\)
\(=\left(\dfrac{5}{7}+\dfrac{-12}{7}\right)+\left(\dfrac{9}{23}+\dfrac{14}{23}\right)\)
\(=-\dfrac{7}{7}+\dfrac{23}{23}\)
\(=\left(-1\right)+1=0\)
\(e,\dfrac{3}{17}+-\dfrac{5}{13}+-\dfrac{18}{35}+\dfrac{14}{17}+\dfrac{17}{-35}+-\dfrac{8}{13}\)
\(=\left(\dfrac{3}{17}+\dfrac{14}{17}\right)+\left(\dfrac{-5}{13}+\dfrac{-8}{13}\right)+\left(\dfrac{-18}{35}+\dfrac{-17}{35}\right)\)
\(=\dfrac{17}{17}+\dfrac{-13}{13}+-\dfrac{35}{35}\)
\(=1+\left(-1\right)+\left(-1\right)=0+\left(-1\right)=-1\)
\(f,\dfrac{-3}{8}. \dfrac{1}{6}+\dfrac{3}{-8}.\dfrac{5}{6}+\dfrac{-10}{16}\)
\(=\dfrac{-3}{8}.\dfrac{1}{6}+\dfrac{-3}{8}.\dfrac{5}{6}+\dfrac{-10}{16}\)
\(=\dfrac{-3}{8}.\left(\dfrac{1}{6}+\dfrac{5}{6}\right)+-\dfrac{10}{16}\)
=\(\dfrac{-3}{8}.1+\dfrac{-10}{16}\)
\(=\dfrac{-3}{8}+\dfrac{-10}{16}\)
\(=\dfrac{-6}{16}+\dfrac{-10}{16}=\dfrac{-16}{16}=-1\)
\(g,\dfrac{-4}{11}.\dfrac{5}{15}.\dfrac{11}{-4}=\dfrac{-4}{11}.\dfrac{5}{15}.\dfrac{-11}{4}\)
\(=\left(\dfrac{-4}{11}.\dfrac{-11}{4}\right).\dfrac{5}{15}\)
\(=1.\dfrac{5}{15}=1.\dfrac{1}{3}=\dfrac{1}{3}\)
\(h,\dfrac{7}{36}-\dfrac{8}{-9}+\dfrac{-2}{3}=\dfrac{7}{36}-\dfrac{-8}{9}+\dfrac{-2}{3}\)
\(=\dfrac{7}{36}-\dfrac{-32}{36}+\dfrac{-24}{36}=\dfrac{7-\left(-32\right)+\left(-24\right)}{36}\)
\(=\dfrac{15}{56}=\dfrac{5}{12}\)
Tick mình nha ^^
18 tháng 8 2021
d.\(\dfrac{5}{7}\)+\(\dfrac{9}{23}\)+\(\dfrac{12}{7}\)+\(\dfrac{14}{23}\)=(\(\dfrac{5}{7}\)+\(\dfrac{12}{7}\))+(\(\dfrac{9}{23}\)+\(\dfrac{14}{23}\))
=\(\dfrac{17}{7}\)+ 1 = \(\dfrac{24}{7}\)
e.\(\dfrac{3}{17}\)+\(\dfrac{-5}{13}\)+\(\dfrac{-18}{35}\)+\(\dfrac{14}{17}\)+\(\dfrac{17}{-35}\)+\(\dfrac{-8}{13}\)
=(\(\dfrac{3}{17}\)+\(\dfrac{14}{17}\))+(\(\dfrac{-5}{13}\)+\(\dfrac{-8}{13}\))+(\(\dfrac{-18}{35}\)+\(\dfrac{17}{-35}\))
= 1+ (-1) + (-1) = -1
f. \(\dfrac{-3}{8}\).\(\dfrac{1}{6}\)+\(\dfrac{3}{-8}\).\(\dfrac{5}{6}\)+\(\dfrac{-10}{16}\)=\(\dfrac{-3}{8}\)(\(\dfrac{1}{6}\)+\(\dfrac{5}{6}\)) + \(\dfrac{-5}{8}\)
=\(\dfrac{-3}{8}\)+\(\dfrac{-5}{8}\)= -1
g. \(\dfrac{-4}{11}\).\(\dfrac{5}{15}\).\(\dfrac{11}{-4}\)=\(\dfrac{5}{15}\)
h.\(\dfrac{7}{36}\)-\(\dfrac{8}{-9}\)+\(\dfrac{-2}{3}\)= \(\dfrac{7}{36}\)-\(\dfrac{-32}{36}\)+\(\dfrac{-24}{36}\)
=\(\dfrac{-49}{36}\)