Question

11B * Tìm số tự nhiên x biết :

a ) 2x³ + 4 = 58         b ) ( 5 - x )⁵ = 32

c ) (5x - 6 )³ = 64          d ) (3x)³ = (2x + 1 )³

Answer 1

a: =>2x³=54

=>x³=27

hay x=3

b: =>5-x=2

hay x=3

c: =>5x-6=4

hay x=2

Answer 2

\(a,2x^3+4=58\)

\(2x^3=58-4\)

\(2x^3=54\)

\(x^3=54:2\)

\(x^3=27\)

\(x^3=3^3\)

\(x=3\)

________________________

\(b,\left(5-x\right)^5=32\)

\(\left(5-x\right)^5=2^5\)

\(5-x=2\)

\(x=5-2\)

\(x=3\)

____________________________

\(c,\left(5x-6\right)^3=64\)

\(\left(5x-6\right)^3=4^3\)

\(5x-6=4\)

\(5x=4+6\)

\(5x=10\)

\(x=10:5\)

\(x=2\)

___________________________

\(d,\left(3x\right)^3=\left(2x+1\right)^3\)

\(3x=2x+1\)

\(3x-2x=1\)

\(\left(3-2\right)x=1\)

\(1.x=1\)

\(x=1:1\)

\(x=1\)

Answer 3

`2x^3+4=58`

`2x^3=58-4`

`2x^3=54`

`x^3=54:2`

`x^3=27`

`x^2=3^3`

`=>x =3`

______________________

`(5-x)^2=32`

`(5-x)^5=2^5`

`5-x=2`

`x=5-2`

`x=3`

________________________

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

`<=> 3x = 2x+1`

`3x-2x=1`

`1x=1`

`x=1:1`

`x=1`