Tính nhanh
C = -1/2 + 3/21 + -2/6 + -5/30
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H9
HT.Phong (9A5)
CTVHS
19 tháng 7 2023
Bài 6:
\(21,251+6,058+0,749+1,042\)
\(=\left(21,251+0,749\right)+\left(6,058+1,042\right)\)
\(=22+7,1\)
\(=29,1\)
___________________
\(1,53+5,309+12,47+5,691\)
\(=\left(1,53+12,47\right)+\left(5,309+5,691\right)\)
\(=14+11\)
\(=25\)
22 tháng 7 2023
5:
a: =>x/17=5/17
=>x=5
b; =>6+x=7/11*33=21
=>x=15
c: \(\dfrac{12+x}{43-x}=\dfrac{2}{3}\)
=>3x+36=86-2x
=>5x=50
=>x=10
d: \(\dfrac{x}{5}< \dfrac{3}{7}\)
=>x<3/7*5
=>x<15/7
f: 15/26+x/16=46/52
=>x/16=23/26-15/26=8/26=4/13
=>x=4/13*16=64/13
25 tháng 3 2015
C = -1/2 +3/21 +-2/6 + -5/30
= -1/2 + 1/7 ( rút gọn 3/21 cho 3 ) + -1/3 (rút gọn cho 2 ) + -1/6 (rút gọn cho 6)
=( -1/2 + -1/3 ) + 1/7 + -1/6
= -5/6 + 1/7 + -1/6
= (-5/6 + -1/6 ) + 1/7
= -1 +1/7
= -7/7 + 1/7
= -6/7
LM
Lê Minh Vũ
VIP
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
\(3\times15+21\times15+85\times5\\ =15\times\left(3+21\right)+425\\ =15\times24+425\\ =360+425\\ =785\)
\(15-30+40\\ =\left(15+40\right)-30\\ =55-30\\ =25\)
\(21+19-50+10\\ =\left(21+19\right)-\left(50-10\right)\\ =40-40\\ =0\)
\(\dfrac{1}{5}-\dfrac{1}{4}+2\)
\(=\dfrac{4}{20}-\dfrac{5}{20}+\dfrac{40}{20}\)
\(=\dfrac{\left(4+40\right)}{20}-\dfrac{5}{20}\)
\(=\dfrac{44}{20}-\dfrac{5}{20}\)
\(=\dfrac{39}{20}\)
\(\left(\dfrac{1}{4}+\dfrac{1}{6}\right)\times\left(\dfrac{1}{2}-\dfrac{1}{4}\right)\)
\(=\dfrac{5}{12}\times\dfrac{1}{4}\)
\(=\dfrac{5}{48}\)
\(\dfrac{1}{10}+\dfrac{1}{5}-\dfrac{3}{4}\)
\(=\dfrac{2}{20}+\dfrac{4}{20}-\dfrac{15}{20}\)
\(=\dfrac{6}{20}-\dfrac{15}{20}\)
\(=-\dfrac{9}{20}\)
1 tháng 4 2022
Bài 2:
a: A=(12,87+14,13)+(-14,7-37,3)
=27-52=-25
b: B=-1/3+2/5-2/3-3/5+1/5
=-1
TD
1
30 tháng 9 2019
A = \(\frac{1}{5\times6}+\frac{3}{6\times9}+\frac{5}{9\times14}+\frac{7}{14\times21}+\frac{9}{21\times30}\)
A = \(\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{9}+\frac{1}{9}-\frac{1}{14}+\frac{1}{14}-\frac{1}{21}+\frac{1}{21}-\frac{1}{30}\)
A = \(1-\frac{1}{30}\)
A = \(\frac{29}{30}\)
\(C=\frac{-1}{2}+\frac{3}{21}+\frac{-2}{6}+\frac{-5}{30}\)
\(C=\frac{-1}{2}+\frac{1}{7}+\frac{-1}{2}+\frac{-1}{6}\)
\(C=\left(\frac{-1}{2}+\frac{-1}{2}\right)+\left(\frac{1}{7}+\frac{-1}{6}\right)\)
\(C=\frac{-2}{2}+\frac{-1}{42}\)
\(C=-1+\frac{-1}{42}\)
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