Bài 4:
`(5/2 + 1/3) : (1 - 2/3) `
`= (15/6 + 2/6) : (3/3 - 2/3) `
`= 17/6 : 1/3`
`= 17/6 xx 3`
`= 17/2`
`(5/2 - 1/3) xx 9/2 - 6/7 `
`= (15/6 - 2/6) xx 9/2 - 6/7 `
`= 13/6 xx 9/2 - 6/7 `
`= 39/4 - 6/7 `
`= 273/28 - 24/28`
`= 249/28`
Bài 5:
`(254 xx 399 - 145)/(254 + 399 xx 253)`
`= ((253 + 1) xx 399 - 145)/(254 + 399 xx 253)`
`= ((253 xx 399 + 399 - 145)/(254 + 399 xx 253)`
`= ((253 xx 399 + 254)/(254 + 399 xx 253)`
`= 1`
`(5932 + 6001 xx 5931 )/( 5932 xx 6001 - 69)`
`= (5932 + 6001 xx 5931 )/( (5931 + 1) xx 6001 - 69)`
`= (5932 + 6001 xx 5931 )/( (5931 xx 6001 + 6001 - 69)`
`= (5932 + 6001 xx 5931 )/( (5931 xx 6001 + 5932)`
`=1 `
Bài 4:
a: \(\left(\dfrac{5}{2}+\dfrac{1}{3}\right):\left(1-\dfrac{2}{3}\right)=\left(\dfrac{15}{6}+\dfrac{2}{6}\right):\dfrac{1}{3}\)
\(=\dfrac{17}{6}\cdot3=\dfrac{17}{2}\)
b: \(\left(\dfrac{5}{2}-\dfrac{1}{3}\right)\cdot\dfrac{9}{2}-\dfrac{6}{7}\)
\(=\dfrac{15-2}{6}\cdot\dfrac{9}{2}-\dfrac{6}{7}\)
\(=\dfrac{13}{2}\cdot\dfrac{3}{2}-\dfrac{6}{7}=\dfrac{39}{4}-\dfrac{6}{7}=\dfrac{249}{28}\)
Bài 5:
a: \(\dfrac{254\cdot399-145}{254+399\cdot253}=\dfrac{253\cdot399+399-145}{253\cdot399+254}\)
\(=\dfrac{253\cdot399+254}{253\cdot399+254}\)
=1
b: \(\dfrac{5932+6001\cdot5931}{5932\cdot6001-69}\)
\(=\dfrac{5932+6001\cdot5932-6001}{5932\cdot6001-69}\)
\(=\dfrac{6001\cdot5932-69}{6001\cdot5932-69}=1\)
a. (5/2 + 1/3) : (1 - 2/3)
= 17/6 : 1/3
= 51/6
b. (5/2 - 1/3) . 9/2 - 6/7
= 13/6 . 9/2 - 6/7
= 13/8 - 6/7
= 43/56
Bài 4:
a) \(\left(\dfrac{5}{2}+\dfrac{1}{3}\right):\left(1-\dfrac{2}{3}\right)\)
\(=\left(\dfrac{15}{6}+\dfrac{2}{6}\right):\left(1-\dfrac{2}{3}\right)\)
\(=\dfrac{17}{6}:\dfrac{1}{3}\)
\(=\dfrac{17}{6}.3\)
\(=\dfrac{51}{6}=\dfrac{27}{2}\)
b) \(\left(\dfrac{5}{2}-\dfrac{1}{3}\right)\times\dfrac{9}{2}-\dfrac{6}{7}\)
\(=\left(\dfrac{15}{6}-\dfrac{2}{6}\right)\times\dfrac{9}{2}-\dfrac{6}{7}\)
\(=\dfrac{13}{6}\times\dfrac{9}{2}-\dfrac{6}{7}\)
\(=\dfrac{39}{4}-\dfrac{6}{7}\)
\(=\dfrac{273}{28}-\dfrac{24}{28}=\dfrac{249}{28}\)
