BÀi 1 :
a, 1/3 + 1/-5 – 1/-6 + -1/8
Bài 2:
a, 5/6 – x +5/-11=-5/6
b, x/5 – 2/3 +3/4 = 17/60
c, 1/8 – 7/5 – 2/x = -233/120 ( x ∈ Z)
BÀi 1 :
a, 1/3 + 1/-5 – 1/-6 + -1/8
Bài 2:
a, 5/6 – x +5/-11=-5/6
b, x/5 – 2/3 +3/4 = 17/60
c, 1/8 – 7/5 – 2/x = -233/120 ( x ∈ Z)
*Lời giải :
Bài 1
`a) 2/3 + 1/(-5) – 1/(-6) + (-1)/8`
`= (2/3 – 1/(-6) ) + (1/(-5) + (-1)/8)`
`= 5/6 + (-13)/40`
`= 61/120`
Bài 2
`a) 5/6 – x + 5/(-11) = (-5)/6`
`-> 5/6 – x = (-5)/6 – 5/(-11)`
`-> 5/6 – x = (-25)/66`
`-> x = 5/6 – (-25)/66`
`-> x = 40/33`
Vậy `x = 40/33`
`b) x/5 – 2/3 + 3/4 = 17/60`
`-> x/5 – 2/3 = 17/60 – 3/4`
`-> x/5 – 2/3 = (-7)/15`
`-> x/5 = (-7)/15 + 2/3`
`-> x/5 = 1/5`
`-> x = 5 . 1/5`
`-> x = 1`
Vậy `x – 1`
`c) 1/8 – 7/5 – 2/x = (-233)/120`
`-> 7/5 – 2/x = 1/8 – (-233)/120`
`-> 7/5 – 2/x= 31/15`
`-> 2/x = 7/5 – 31/15`
`-> 2/x = (-2)/3`
`-> 2 = x . (-2)/3`
`-> x = 2 : (-2)/3`
`-> x = -3 (TM)`
Vậy `x = -3`
Bài 1:
a) `1/3` + `1/-5` – `1/-6` +`-1/8`
= `1/3` + `1/-5` + `-1/6` + `-1/8`
= (`1/3` + `-1/6) + (`1/-5` + `-1/8`)
= (`2/6` + `-1/6`) + (`8/40` + `-5/40`)
= `1/6` + `3/40`
= `20/120` + `9/120`
= `29/120`
Bài 2:
a) `5/6` – x + `5/-11` = `-5/6`
⇒ x + `5/-11` = `5/6` – `-5/6`
⇒ x + `5/-11` = `-5/3`
⇒x = `-5/3` – `5/-11`
⇒x = `-40/33`
Vậy: x= `-40/33`
b, `x/5` – `2/3` + `3/4` =` 17/60`
⇒`x/5` – `2/3` = `17/60` – `3/4`
⇒`x/5` – `2/3` = `-28/60`
⇒`x/5` = `-28/60` + `2/3`
⇒`x/5` = `12/60`
⇒`x/5 = `1/5`
⇒x=1
Vậy: x = 1
c, `1/8` – `7/5` – `2/x` = `-233/120`
⇒`7/5` – `2/x` = `1/8` – `-233/120`
⇒`7/5` – `2/x` = `248/120`
⇒ `7/5` – `2/x` = `31/15`
⇒`-2/x` = `7/5` – `31/15`
⇒`-2/x` = `-10/15`
⇒`-2/x` = `-2/3`
⇒x = 3
Vậy x=3
———–Hết————–
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