`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 !