tìm x biết 45-x/1968 + 40-x/1973 +35-x/1978+ 30-x/1983= -4
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Suy ra các số hang =-1
45-x =-1968
suy ra x = 2013
Vậy x =2013
Đề sai:
\(\dfrac{45-x}{1968}+\dfrac{40-x}{1973}+\dfrac{35-x}{1978}+\dfrac{30-x}{1983}=-4\)
\(\Rightarrow\left(\dfrac{45-x}{1968}+1\right)+\left(\dfrac{40-x}{1973}+1\right)+\left(\dfrac{35-x}{1978}+1\right)+\left(\dfrac{30-x}{1983}+1\right)=0\)
\(\Rightarrow\dfrac{2013-x}{1968}+\dfrac{2013-x}{1973}+\dfrac{2013-x}{1978}+\dfrac{2013-x}{1983}=0\)
\(\Rightarrow\left(2013-x\right)\left(\dfrac{1}{1968}+\dfrac{1}{1973}+\dfrac{1}{1978}+\dfrac{1}{1983}\right)=0\)
Vì \(\dfrac{1}{1968}+\dfrac{1}{1973}+\dfrac{1}{1978}+\dfrac{1}{1983}\ne0\) nên \(2013-x=0\Leftrightarrow x=2013\)
\(\frac{45-x}{1968}+\frac{40-x}{1973}+\frac{35-x}{1978}+\frac{30-x}{1983}=0\)
Vì \(\frac{1}{1968}+\frac{1}{1973}+\frac{1}{1978}+\frac{1}{1983}\ne0\)
\(\Rightarrow2013-x=0\)
\(\Rightarrow x=2013-0\)
\(\Rightarrow x=2013\)
Vậy \(x=2013.\)
Chúc bạn học tốt!
45-x/1963+40-x/1968+35-x/1973+30-x/1978+4=0
45-x/1963+40-x/1968+35-x/1973+30-x/1978=-4
(45-x/1963+1)+(40-x/1968+1)+(35-x/1973+1)+(30-x/1978+1)=-4+1+1+1+1
2008-x/1963+2008-x/1968+2008-x/1973+2008-x/1978=0
(2008-x).(1/1963+1/1968+1/1973+1/1978)=0
Vì 1/1963+1/1968+1/1973+1/1978 khac o
2008-x=0
x=2008
k cho minh dau tien nha!
\(\frac{45-x}{1963}+\frac{40-x}{1968}+\frac{35-x}{1973}+\frac{30-x}{1978}=-4\)
\(\left(\frac{45-x}{1963}+1\right)+\left(\frac{40-x}{1968}+1\right)+\left(\frac{35-x}{1973}+1\right)+\left(\frac{30-x}{1978}+1\right)=0\)
\(\frac{2008-x}{1963}+\frac{2008-x}{1968}+\frac{2008-x}{1973}+\frac{2008-x}{1978}=0\)
\(\left(2008-x\right)\left(\frac{1}{1963}+\frac{1}{1968}+\frac{1}{1973}+\frac{1}{1978}\right)=0\)
=> 2008 - x = 0 ( vì 1/ 1963 + ... khác 0 )
=> x = 2008
196345−x+196840−x+197335−x+197830−x=−4
\left(\frac{45-x}{1963}+1\right)+\left(\frac{40-x}{1968}+1\right)+\left(\frac{35-x}{1973}+1\right)+\left(\frac{30-x}{1978}+1\right)=0(196345−x+1)+(196840−x+1)+(197335−x+1)+(197830−x+1)=0
\frac{2008-x}{1963}+\frac{2008-x}{1968}+\frac{2008-x}{1973}+\frac{2008-x}{1978}=019632008−x+19682008−x+19732008−x+19782008−x=0
\left(2008-x\right)\left(\frac{1}{1963}+\frac{1}{1968}+\frac{1}{1973}+\frac{1}{1978}\right)=0(2008−x)(19631+19681+19731+19781)=0
=> 2008 - x = 0 ( vì 1/ 1963 + ... khác 0 )
=> x = 2008
Ta có : \(\frac{45-x}{1963}+\frac{40-x}{1968}+\frac{35-x}{1973}+\frac{30-x}{1978}+4=0\)
\(\Leftrightarrow\frac{45-x}{1963}+1+\frac{40-x}{1968}+1+\frac{35-x}{1973}+1+\frac{30-x}{1978}=0\)
\(\Leftrightarrow\frac{2008-x}{1963}+\frac{2008-x}{1968}+\frac{2008-x}{1973}+\frac{2008-x}{1978}=0\)
\(\Leftrightarrow\left(2008-x\right)\left(\frac{1}{1963}+\frac{1}{1968}+\frac{1}{1973}+\frac{1}{1978}\right)=0\)
Vì \(\left(\frac{1}{1963}+\frac{1}{1968}+\frac{1}{1973}+\frac{1}{1978}\right)\ne0\)
Nên : 2008 - x = 0
<=> x = 2008
Vậy x = 2008