Question

11B * Tìm số tự nhiên x biết :

a ) 2x³ + 4 = 58

b ) (5x - 6 )³ = 64

c ) (3x)³ = (2x + 1 )³

Answer 1

c: =>3x=2x+1

=>x=1

a: =>2x³=54

=>x³=27

hay x=3

b: =>5x-6=4

=>5x=10

hay x=2

Answer 2

`2x^3+4=58`

`2x^3=58-4`

`2x^3=54`

`x^3=54:2`

`x^3=27`

`x^2=3^3`

`=>x =3`

__________________________

`(5x-6)^3 = 64`

`(5x-6)^3 = 4^3`

`5x-6=4`

`5x=6+4`

`5x=10`

`x=10:5`

`x=2`

________________

`(3x)^3 = (2x+1)^3`

`3x=2x+1`

`3x-2x=1`

`(3-2)x=1`

`1x=1`

`=> x = 1`