Tính nhanh : a, 11/125 – 17/18 – 5/7 + 4/9 + 17/14 b, 1 – 1/2 + 2 – 2/3 + 3 – 3/4 + 4 – 1/4 – 3 – 1/3 – 2 – 1/2 – 1

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Tính nhanh :
a, 11/125 – 17/18 – 5/7 + 4/9 + 17/14
b, 1 – 1/2 + 2 – 2/3 + 3 – 3/4 + 4 – 1/4 – 3 – 1/3 – 2 – 1/2 – 1

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  1. `a,11/125 – 17/18 – 5/7 + 4/9 + 17/14`

    `= 1927/2250 – 5/7 + 209/126`

    `= 1927/2250 + 17/18`

    `= 11/125`

    `b`$1-\dfrac{1}{2}+2-\dfrac{2}{3}+3-\dfrac{3}{4}+4-\dfrac{1}{4}-3-\dfrac{1}{3}-2-\dfrac{1}{2}-1\\ =\left(1-1\right)-\left(\dfrac{1}{2}+\dfrac{1}{2}\right)+\left(2-2\right)-\left(\dfrac{2}{3}+\dfrac{1}{3}\right)+\left(3-3\right)-\left(\dfrac{3}{4}+\dfrac{1}{4}\right)-1\\ =-1-1-1+4\\= 1$

    Xin hay nhất !

     

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