`a, 5 . (5 - x) = -27 - 8`
`5 . (5 - x) = -35`
`5 - x= -35 : 5`
`5 - x = -7`
`x = 5 - (-7)`
`x = 12`
Vậy: `x = 12`
`b, 3^(x - 2) - 7 = 2^2 . 5`
`3^(x - 2) - 7 = 4 . 5`
`3^(x - 2) - 7 = 20`
`3^(x - 2) = 20 + 7`
`3^(x- 2) = 27`
`3^(x - 2) = 3^3`
`x - 2 = 3`
`x = 3 + 2`
`x=5`
Vậy: `x=5`
a)5.(5−x)=−27−8
⇒5.(5−x)=−35
⇒5−x=−7
⇒x=12∈Z(tm)
Vậy x=12
b)3x−2−7=22.5
⇒3x−2−7=4.5
⇒3x−2−7=20
⇒3x−2=27
⇒3x−2=33
⇒x−2=3
⇒x=5∈Z(tm)
Vậy x=5