a)4x³+15=47

4x³=47-15

4x³=32

x³=32:4

x³=8

x³=2³​

vậy x = 2

b)4.2^x-3=125

4.2^x=125+3

​4.2^x=128

​2^x=128:4

2^x=32

2^x=2⁵

Vậy x=5

a) 4x³ + 15 = 47                                       b) 4.2^x - 3 = 125

    4x³        = 47 - 15                                     4.2^x      = 125 + 3

    4x³        = 32                                            4.2^x      = 128

      x³        = 32 : 4                                           2^x     = 128 : 4

      x³        = 8                                                  2^x     = 32

      x³        = 2³                                                    2^x     = 2⁵

  => x         = 2                                            =>   x     = 5

a) x=2

b) x=5

a)x=2

b)x=5

học tốt

a, \(4x^2+15=47\\ =>4x^2=47-15=32\\ =>x^2=32:4=8\\ =>x\ne N\)

b, \(4.2^x-3=125\\ =>4.2^x=125+3=128\\ =>2^x=128:4=32\\ Mà:2^5=32\\ =>x=5\)

a) 4\(x^2\)+ 15 = 47

=> 4\(x^2\) = 47 - 15

=> 4\(x^2\)= 32

=> \(x^2\)= 32 : 4

=> \(x^2\)= 8

=> \(x\) \(\ne\) N

b) 4. \(2^x\) - 3 = 125

=> 4.2\(^x\)= 125 + 3

=> 4. \(2^x\)= 128

=> \(2^x\)= 128 : 4

=> \(2^x\)= 32

Mà \(2^5\) = 32 nên \(x\) = 5

\(4x^3+15=47\)

\(\Leftrightarrow4x^3=32\)

\(\Leftrightarrow x^3=8\)

\(\Leftrightarrow x^3=2^3\)

\(\Leftrightarrow x=2\)

\(4.2^x-3=125\)

\(\Leftrightarrow4.2^x=128\)

\(\Leftrightarrow2^x=32\)

\(\Leftrightarrow2^x=2^5\)

\(\Leftrightarrow x=5\)

ok thanks

a) \(128-3\left(x+4\right)=23\)

\(\Rightarrow3\left(x+4\right)=128-23\)

\(\Rightarrow3\left(x+4\right)=105\)

\(\Rightarrow x+4=35\)

\(\Rightarrow x=35-4\)

\(\Rightarrow x=31\)

b) \(\left[\left(4x+28\right)\cdot3+55\right]:5=35\)

\(\Rightarrow\left(4x+28\right)\cdot3+55=35\cdot5\)

\(\Rightarrow\left(4x+28\right)\cdot3+55=175\)

\(\Rightarrow\left(4x+28\right)\cdot3=120\)

\(\Rightarrow4x+28=40\)

\(\Rightarrow4x=12\)

\(\Rightarrow x=3\)

a, \(128-3\left(x+4\right)=23\)

\(=>3\left(x+4\right)=128-23\)

\(=>3\left(x+4\right)=105\)

\(=>x+4=105:3\)

\(=>x+4=35\)

\(=>x=35-4\)

\(=>x=31\)

b, \(\left[\left(4x+28\right).3+55\right]:5=35\)

\(=>\left(4x+28\right).3+55=35.5\)

\(=>\left(4x+28\right).3+55=175\)

\(=>\left(4x+28\right).3=175-55\)

\(=>\left(4x+28\right).3=120\)

\(=>4x+28=120:3\)

\(=>4x+28=40\)

\(=>4x=40-28\)

\(=>4x=12\)

\(=>x=12:4\)

\(=>x=3\)

\(#WendyDang\)

a  21-4x=13
  -4x=13-21
-4x=-8
x=-8/-4
x=2
 

b x=5