\(1-\dfrac{1}{2}+2-\dfrac{2}{3}+3-\dfrac{3}{4}+4-\dfrac{1}{4}-3-\dfrac{1}{3}-2-\dfrac{1}{2}-1\)
\(=-\dfrac{1}{2}-\dfrac{1}{2}-\dfrac{2}{3}-\dfrac{1}{3}-\dfrac{3}{4}-\dfrac{1}{4}=-1-1-1+4=-3+4=1\)
Vậy..........................
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\(1-\dfrac{1}{2}+2-\dfrac{2}{3}+3-\dfrac{3}{4}+4-\dfrac{1}{4}-3-\dfrac{1}{3}-2-\dfrac{1}{2}-1\)
=\(\left(1+2+3+4-3-2-1\right)-\left(\dfrac{1}{2}+\dfrac{2}{3}+\dfrac{3}{4}+\dfrac{1}{4}+\dfrac{1}{3}+\dfrac{1}{2}\right)\)
= 4 - 3
= 1
\(1-\dfrac{1}{2}+2-\dfrac{2}{3}+3-\dfrac{3}{4}+4-\dfrac{1}{4}-3-\dfrac{1}{3}-2-\dfrac{1}{2}-1\\ =\left(1-1\right)-\left(\dfrac{1}{2}+\dfrac{1}{2}\right)+\left(2-2\right)-\left(\dfrac{2}{3}+\dfrac{1}{3}\right)+\left(3-3\right)-\left(\dfrac{3}{4}+\dfrac{1}{4}\right)-1\\ =-1-1-1+4=1\)
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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=(1-1)+(2-2)+(3-3)+(-\(\dfrac{1}{2}\)-\(\dfrac{1}{2}\))+(-\(\dfrac{2}{3}\)-\(\dfrac{1}{3}\))+(-\(\dfrac{3}{4}\)-\(\dfrac{1}{4}\))+4=0+0+0+(-1)+(-1)+(-1)+4=1
= (1+2+3+4-3-2-1) + (-1/2-2/3-3/4-1/4-1/3-1/2)
= 4 + ( -3) =1
