tìm số nguyên x ,biết a)210-5 .(x-9)+195 b) 450:[41-(2x+5)= 3^2 .5 c) x^2=4 d)x^3-1=7 e)2x^3-6=10 f)2x^2-8=10

`a)` `210 - 5 . (x - 9) = 195`

`⇔ 5 . (x - 9) = 15`

`⇔ x - 9  = 3`

`⇔ x       = 12`

`b)` `450 : [41 - (2x - 5)] = 3^2 . 5`

`⇔ 450 : [41 - 2x + 5] = 9 . 5`

`⇔ 450 : [46 - 2x] = 45`

`⇔ 46 - 2x = 10`

`⇔ 2x = 36`

`⇔ x = 18`

`c)` `x^2=4`

`⇔x^2−4=0`

`=> x = ±2`

`d)` `x^3-1=7`

`⇔x^3=8`

`=>x=2`

`e)` `2x^3-6=10`

`⇔2x^3=16`

`⇔x^3=8`

`=> x=2`

`f)` `2x^2-8=10`

`⇔2x^2-18=0`

`⇔x^2-9=0`

`=>x=±3`

$\text{@dieulinh2k7~~}$

$a)$

$210-5.(x-9)=195$

$⇒5.(x-9)=210-195$

$⇒5.(x-9)=15$

$⇒x-9=15:5$

$⇒x-9=3$

$⇒x=3+9$

$⇒x=12$

$\text{Vậy $x=12$}$

$b)$

$450:[41-(2x+50)]=3^2.5$

$⇒450:[41-(2x+50)]=45$

$⇒41-(2x+50)=450:45$

$⇒41-(2x+50)=40$

$⇒2x+50=41-40$

$⇒2x+50=1$

$⇒2x=-49$        

$⇒x=-49:2$

$⇒x=-24,5$

$\text{Vậy $x=-24,5$}$

$c)$

$x^2=4$

$⇒x^2=2^2$

$⇒x=2$

$\text{Vậy $x=2$}$

$d)$

$x^3-1=7$

$⇒x^3=7+1$

$⇒x^3=8$

$⇒x^3=2^3$

$⇒x=2$

$\text{Vậy $x=2$}$

$e)$

$2x^3-6=10$

$⇒2x^3=10+6$

$⇒2x^3=16$

$⇒x^3=16:2$

$⇒x^3=8$

$⇒x^3=2^3$

$⇒x=2$

$\text{Vậy $x=2$}$

$f)$

$2x^2-8=10$

$⇒2x^2=10+8$

$⇒2x^2=18$

$⇒x^2=18:2$

$⇒x^2=9$

$⇒x^2=3^2$

$⇒x=3$

$\text{Vậy $x=3$}$