1/2x-75%=1/4 |x-2/3|+0,25=3/4 M=4/1×3+4/3×5+4/5×7+….+4/2011×2013

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1. 1/2x-75%=1/4

   =>2x-3/4=1/4

   =>2x=1/4+3/4

   =>2x=1

   =>x=1/2

   Vậy x=1/2

   2,|x-2/3|+0,25=3/4

   =>|x-2/3|+1/4=3/4

   =>|x-2/3|=3/4-1/4

   =>|x-2/3|=1/2

   =>x-2/3=1/2 hoặc x-2/3=-1/2

   =>x=1/2+2/3 hoặc x=-1/2+2/3

   =>x=7/6 hoặc x=1/6

   3,M=4/1×3+4/3×5+4/5×7+….+4/2011×2013

   =2.(2/1.3+2/3.5+2/5.7+…+2/2011.2013)

   =2.(1-1/3+1/3-1/5+1/5-1/7+…+1/2011-1/2013)

   =2.(1-1/2013)

   =2.2012/2013

   =4024/2013

    

   Trả lời

2. `1/2x-75%=1/4`

   `<=>1/2x=1/4+3/4`

   `<=>x=1-:1/2`

   `<=>x=2`

   `|x-2/3|+0,25=3/4`

   `<=>|x-2/3|=3/4-1/4=1/2`

   \(⇔\left[ \begin{array}{l}x-\dfrac23=\dfrac12\\x-\dfrac23=\dfrac{-1}2\end{array} \right.⇔\) \(\left[ \begin{array}{l}x=\dfrac76\\x=\dfrac16\end{array} \right.\)

   `text{Vậy }x={7/6;1/6}`

   `M=4/(1×3)+4/(3×5)+4/(5×7)+….+4/(2011×2013)`

   `M=2(2/(1×3)+2/(3×5)+2/(5×7)+….+2/(2011×2013))`

   `M=2(1-1/3+1/3-1/5+1/5-1/7+…+1/2011-1/2013)`

   `M=2(1-1/2013)`

   `M=2xx2012/2013`

   `M=4024/2013`

   `(-1/2)^2+5/8÷(-5)/2`

   `=1/4+5/8xx2/-5`

   `=1/4+(-1)/4`

   `=0`

   Trả lời