1980 x 123 = ???
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YL
2
DT
19 tháng 6 2018
1987 x 1979 + 1980 x 21 + 1958 / 1980 x 1979 - 1978 x 1979
= 1987 x 21 + 1958 / 1979 - 1978
= 41727 + 1958 / 1
= 43685 / 1 = 43685
DT
Dang Tung
CTVHS
23 tháng 1 2023
\(\dfrac{x-5}{1990}+\dfrac{x-15}{1980}=\dfrac{x-1990}{5}+\dfrac{x-1980}{15}\\ =>\dfrac{x-5}{1990}-1+\dfrac{x-15}{1980}-1=\dfrac{x-1990}{5}-1+\dfrac{x-1980}{15}-1\\ =>\dfrac{x-1995}{1990}+\dfrac{x-1995}{1980}-\dfrac{x-1995}{5}-\dfrac{x-1995}{15}=0\\ =>\left(x-1995\right).\left(\dfrac{1}{1990}+\dfrac{1}{1980}-\dfrac{1}{5}-\dfrac{1}{15}\right)=0\\ =>x-1995=0\\ =>x=1995\)
LT
1
TN
19 tháng 6 2016
d) x-5/1990 + x+5/1980 + x-25/1970=x-1990/5 + x-1980/15
\(\Leftrightarrow\left(\frac{x-5}{1990}-1\right)+\left(\frac{x-15}{1980}-1\right)+\left(\frac{x-25}{1970}-1\right)=\left(\frac{x-1990}{5}-1\right)+\left(\frac{x-1980}{15}-1\right)+\left(\frac{x-1970}{25}-1\right)\)
\(\Leftrightarrow\frac{x-1995}{1990}+\frac{x-1995}{1980}+\frac{x-1995}{1970}=\frac{x-1995}{5}+\frac{x-1995}{15}+\frac{x-1995}{25}\).
\(\Leftrightarrow\frac{x-1995}{1990}+\frac{x-1995}{1980}+\frac{x-1995}{1970}-\frac{x-1995}{5}+\frac{x-1995}{15}+\frac{x-1995}{25}=0\)
\(\Leftrightarrow\left(x-1995\right)\left(\frac{1}{1990}+\frac{1}{1980}+\frac{1}{1970}-\frac{1}{5}+\frac{1}{15}+\frac{1}{25}\right)=0\)
\(\Leftrightarrow x-1995=0\).Do \(\frac{1}{1990}+\frac{1}{1980}+\frac{1}{1970}-\frac{1}{5}+\frac{1}{15}+\frac{1}{25}\ne0\)
\(\Leftrightarrow x=1995\)
H
3
13 tháng 3 2018
pt <=> (x-5/1990 - 1) + (x-15/1980 - 1) = (x-1980/15 - 1) + (x-1990/5 - 1)
<=> x-1995/1990 + x-1995/1980 = x-1995/15 + x-1995/5
<=> x-1995/15 + x-1995/5 - x-1995/1990 - x-1995/1980 = 0
<=> (x-1995).(1/5+1/15-1/1990-1/1980) = 0
<=> x-1995 = 0 ( vì 1/5 + 1/15 - 1/1990 - 1/1980 > 0 )
<=> x = 1995
Vậy S={1995}
Tk mk nha
13 tháng 3 2018
Ta có :
\(\frac{x-5}{1990}+\frac{x-15}{1980}=\frac{x-1980}{15}+\frac{x-1990}{5}\)
\(\Leftrightarrow\)\(\left(\frac{x-5}{1990}-1\right)+\left(\frac{x-15}{1980}-1\right)=\left(\frac{x-1980}{15}-1\right)+\left(\frac{x-1990}{5}-1\right)\)
\(\Leftrightarrow\)\(\frac{x-1995}{1990}+\frac{x-1995}{1980}=\frac{x-1995}{15}+\frac{x-1995}{5}\)
\(\Leftrightarrow\)\(\frac{x-1995}{1990}+\frac{x-1995}{1980}-\frac{x-1995}{15}-\frac{x-1995}{5}=0\)
\(\Leftrightarrow\)\(\left(x-1995\right)\left(\frac{1}{1990}+\frac{1}{1980}+\frac{1}{15}+\frac{1}{5}\right)=0\)
Vì \(\frac{1}{1990}+\frac{1}{1980}+\frac{1}{15}+\frac{1}{5}\ne0\)
Nên \(x-1995=0\)
\(\Rightarrow\)\(x=1995\)
Vậy \(x=1995\)
Chúc bạn học tốt ~
20 tháng 6 2017
90 + 90 = 180
2 x 2 = 4
9 x 9 = 81
8 x 8 = 64
200 x 1860 = 336 000
89 x 22 = 1958
88 x 11 = 968
1980 x 1980 + 1980 x 2980 = 9 820 800
20000 x 400 = 8 000 000
9960 x 2235 = 22 260 600
DA
20 tháng 6 2017
90 + 90 = 180
2 x 2 = 4
9 x 9 = 81
8 x 8 = 64
200 x 1860 = 372000
89 x 22 = 1958
88 x 11 = 968
1980 x 1980 + 1980 x 2980 = 9820800
20000 x 400 = 8000000
9960 x 2235 =22260600
k mik nha
chúc bạn hok giỏi
PT
5 tháng 7 2018
\(\dfrac{x-5}{1990}+\dfrac{x-15}{1980}=\dfrac{x-1980}{15}+\dfrac{x-1990}{5}\)
\(\Leftrightarrow(\dfrac{x-5}{1990}-1)+(\dfrac{x-15}{1980}-1)=(\dfrac{x-1980}{15}-1)+(\dfrac{x-1990}{5}-1)\)
\(\Leftrightarrow\dfrac{x-1995}{1990}+\dfrac{x-1995}{1980}-\dfrac{x-1995}{15}-\dfrac{x-1995}{5}=0\)
\(\Leftrightarrow\left(x-1995\right)\left(\dfrac{1}{1990}+\dfrac{1}{1980}-\dfrac{1}{15}-\dfrac{1}{5}\right)=0\)
\(\Leftrightarrow x-1995=0\)
\(\Leftrightarrow x=1995\)
5 tháng 7 2018
\(Giải\):
\(\dfrac{x-5}{1990}\)+\(\dfrac{x-15}{1990}\)=\(\dfrac{x-1980}{15}\)+\(\dfrac{x-1990}{5}\)
⇔(\(\dfrac{x-5}{1990}\)- 1) + (\(\dfrac{x-15}{1980}\)- 1) = (\(\dfrac{x-1980}{15}\)-1) +\(\dfrac{x-1990}{5}\) - 1)
⇔ \(\dfrac{x-1995}{1990}\)+\(\dfrac{x-1995}{1980}\)-\(\dfrac{x-1995}{15}\)-\(\dfrac{x-1995}{5}\)= 0
⇔ (\(x-1995\)) (\(\dfrac{1}{1990}\)+\(\dfrac{1}{1980}\)-\(\dfrac{1}{15}\)-\(\dfrac{1}{5}\)) = 0
⇔\(x-1995=0\)
⇔\(x=1995\)
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