Tính nhanh:
(1/3-5/6)^2:-5/12-1,15
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LM
1
30 tháng 7 2015
Ta có thể đổi chỗ các phân số :
A)(7/12+5/12)+(4/9+1/3)+2=12/12+7/9+2=1+2+7/9=3+7/9=34/9
B)6/5*(3/8+5/8)-4/5=6/5*1-4/5=6/5-4/5=2/5
BD
10
HM
16 tháng 3 2016
1+2+3+4+5+6+7+8+9+10+11+12+13-1-2-3-4-5-6-7-8-9-10-11-12
=(1-1)+(2-2)+(3-3)+(4-4)+(5-5)+(6-6)+(7-7)+(8-8)+(9-9)+(10-10)+(11-11)+(12-12)+13
= 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 13
= 13
16 tháng 3 2016
1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 + 12 + 13 - 1 - 2 - 3 - 4 - 5 - 6 - 7- 8 - 9 - 10
= (1+12) + (2+11) + (3+10) + ( 4+9) + (5+8) + (6+7) + 13 - (1+11) - ( 2+10) - ( 3+9) - (4+8) - (5+7) + 6 + 12
= 13 * 7 - 12 * 6 + 6
= 13
Ai k mk mk k lại
QT
1
4 tháng 3 2023
`1/2+2/4+3/6+4/8+5/10+6/12`
`=1/2+1/2+1/2+1/2+1/2+1/2`
`=1/2*6=3`
`1/3+1/4+1/5+8/10+20/15+20/30`
`=(1/3+1/4)+(1/5+4/5)+(4/3+2/3)`
`=7/12+1+2`
`=7/12+3=43/12`
S
4 tháng 3 2023
\(\dfrac{1}{2}+\dfrac{2}{4}+\dfrac{3}{6}+\dfrac{4}{8}+\dfrac{5}{10}+\dfrac{6}{12}\)
\(=\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{2}\)
\(=\dfrac{1}{2}\times6=3\)
\(------\)
\(\dfrac{1}{3}+\dfrac{1}{4}+\dfrac{1}{5}+\dfrac{8}{10}+\dfrac{20}{15}+\dfrac{20}{30}\)
\(=\dfrac{1}{3}+\dfrac{1}{4}+\dfrac{1}{5}+\dfrac{4}{5}+\dfrac{4}{3}+\dfrac{2}{3}\)
\(=\left(\dfrac{1}{3}+\dfrac{4}{3}+\dfrac{2}{3}\right)+\left(\dfrac{1}{5}+\dfrac{4}{5}\right)+\dfrac{1}{4}\)
\(=\dfrac{7}{3}+1+\dfrac{1}{4}\)
\(=\dfrac{28}{12}+\dfrac{12}{12}+\dfrac{3}{12}\)
\(=\dfrac{43}{12}\)
LT
20 tháng 6 2021
a) \(5+\dfrac{2}{3}=\dfrac{15}{3}+\dfrac{2}{3}=\dfrac{17}{3}\)
b) \(\dfrac{12}{5}\cdot\dfrac{1}{4}=\dfrac{3}{5}\)
c) \(\dfrac{3}{8}-\dfrac{1}{3}=\dfrac{9}{24}-\dfrac{8}{24}=\dfrac{1}{24}\)
d) \(\dfrac{6}{15}-\dfrac{1}{3}:\dfrac{5}{3}=\dfrac{6}{15}-\dfrac{1}{3}\cdot\dfrac{3}{5}=\dfrac{6}{15}-\dfrac{1}{5}=\dfrac{6}{15}-\dfrac{3}{15}=\dfrac{3}{15}=\dfrac{1}{5}\)
20 tháng 6 2021
\(5+\dfrac{2}{3}=\dfrac{5}{1}+\dfrac{2}{3}=\dfrac{15}{3}+\dfrac{2}{3}=\dfrac{17}{9};\dfrac{12}{5}x\dfrac{1}{4}=\dfrac{12}{40};\dfrac{3}{8}-\dfrac{1}{3}=\dfrac{9}{24}-\dfrac{8}{24}=\dfrac{1}{24}\)
Lời giải:
Ta có:
\(A=\left(\frac{1}{3}-\frac{5}{6}\right)^2:(-\frac{5}{12})-1,15\)
\(A=\left(\frac{2-5}{6}\right)^2:(-\frac{5}{12})-1,15\)
\(A=\left(-\frac{1}{2}\right)^2:(-\frac{5}{12})-1,15\)
\(A=\frac{1}{4}:(-\frac{5}{12})-1,15\)
\(A=-\frac{3}{5}-1,15\)
\(A=-0,6-1,15\)
\(A=-1,75\)
\(\left(\frac{1}{3}-\frac{5}{6}\right)^2:\left(-\frac{5}{12}\right)-1,15\)
\(=\left(-\frac{1}{2}\right)^2:\left(-\frac{5}{12}\right)-\frac{23}{20}\)
\(=\frac{1}{4}:\left(-\frac{5}{12}\right)-\frac{23}{20}\)
\(=\left(-\frac{3}{5}\right)-\frac{23}{20}\)
\(=-\frac{7}{4}.\)
Chúc bạn học tốt!