a , 5/18

b, -4/25

c, 0

hook tốt

a)25/42-20/63=5/18

b)9/50-13/75-1/6=-4/25

c)2/15-2/65-4/39=0

bạn có thể giải chi tiết ko viết thế đi thi trừ hết điểm

giúp mình với bài này hơ khó :Tìm x và y biết :x/2=3/y=2/4

a) 25/42 - 20/63 = 5/18

b) ( 9/50 - 13/75 - 1/6 ) : ( -1/2 )² = -16/25

c) ( 2/15 - 2/65 - 4/39 ) : ( 1/2 - 1/3 )² = 0

kick và kết bạn với mình nha

\(\frac{25}{12}-\frac{20}{63}=\frac{445}{252}\)

\(\frac{9}{50}-\frac{13}{75}=\frac{1}{150}\)

\(\frac{2}{19}-\frac{2}{65}-\frac{4}{39}=\frac{-8}{285}\)

`@` `\text {Ans}`

`\downarrow`

`a)`

`13/50 + 9% + 41/100 + 0,24`

`= 0,26 + 0,09 + 0,41 + 0,24`

`= (0,26 + 0,24) + (0,09 + 0,41)`

`= 0,5 + 0,5`

`= 1`

`b)`

`2018 \times 2020 - 1/2017 + 2018 \times 2019`

`= 2018 \times (2020 + 2019) - 1/2017`

`= 2018 \times 4039 - 1/2017`

`= 8150702`

`c)`

`1/2 + 1/6 + 1/12 + 1/20 +1/30 +1/42`

`=`\(\dfrac{1}{1\times2}+\dfrac{1}{2\times3}+\dfrac{1}{3\times4}+\dfrac{1}{4\times5}+\dfrac{1}{5\times6}+\dfrac{1}{6\times7}\)

`=`\(1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{6}-\dfrac{1}{7}\)

`=`\(1-\dfrac{1}{7}\)

`= 6/7`

\(a,\dfrac{13}{50}+9\%+\dfrac{41}{100}+0,24\\ 0,26+0,09+0,41+0,24\\ =\left(0,26+0,24\right)+\left(0,09+0,41\right)\\ =0,5+0,5\\ =1\\ b,2018\times2020-\dfrac{1}{2017}+2018\times2019\\ =2018\times\left(2020+2019\right)-\dfrac{1}{2017}\\ =2018\times4039-\dfrac{1}{2017}\\ =3150702-\dfrac{1}{2017}\\ c,\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}\\ =1-\dfrac{1}{2}+\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+\dfrac{1}{4\cdot5}+\dfrac{1}{5\cdot6}+\dfrac{1}{6\cdot7}\\ =1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}.........+\dfrac{1}{6}-\dfrac{1}{7}\\ =1-\dfrac{1}{7}\\ =\dfrac{6}{7}\)

Cảm ơn các bạn đã trả lời giúp mình câu hỏi nha

a,\(\frac{25}{42}-\frac{20}{63}=\frac{5}{18}\)

b,\(\frac{9}{50}-\frac{13}{75}-\frac{1}{6}\)

=\(\frac{1}{150}-\frac{1}{6}\)

=\(-\frac{4}{25}\)

c,\(\frac{2}{15}+\frac{-2}{65}-\frac{4}{39}\)

=\(\frac{32}{195}-\frac{4}{39}\)

=\(\frac{4}{65}\)

a,=75/126-40/126=35/126=5/18

b,=27/150-26/150-25/150=-4/25

c,=26/195+-6/195-20/195=0

a)\(\dfrac{25}{42}-\dfrac{20}{36}=\dfrac{900}{1512}-\dfrac{840}{1512}=\dfrac{60}{1512}=\dfrac{5}{126}\)

b)\(\dfrac{9}{50}-\dfrac{13}{75}-\dfrac{1}{6}=\dfrac{4050}{22500}-\dfrac{3900}{22500}-\dfrac{3750}{22500}=\dfrac{-3600}{22500}=\dfrac{-4}{25}\)

a) -1/4

b)10/11(-8/9+7/18)=10/11.(-1/2)=-5/11

c) 3/14.28-13/21.28+29/42.28-8=28(3/14-13/21+29/42)-8=28.2/7-8=8-8=0