giải phương trình

T

trinhminh18

x-5/1990 + x-15/1980 + x-25/1970 = x-1990/5 + x-1980/15 + x-1970/25
Giải:
Ta có $\dfrac{x-5}{1990}$-1+$\dfrac{x-15}{1980}$-1+$\dfrac{x-25}{1970}$-1=
$\dfrac{x-1990}{5}$-1+ $\dfrac{x-1980}{15}$-1+ $\dfrac{x-1970}{25}$-1
\Leftrightarrow(x-1995).( $\dfrac{1}{1990}$+ $\dfrac{1}{1980}$+ $\dfrac{1}{1970}$- $\dfrac{1}{5}$- $\dfrac{1}{15}$- $\dfrac{1}{25}$)=0
\Leftrightarrow$x-1995=0$
\Leftrightarrow$x=1995$
 
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