a)
\(4x^3+15=47\)
\(4x^3=32\)
\(x^3=8=2^3\Rightarrow x=2\)
b)
\(4\cdot2^x-3=125\)
\(4\cdot2^x=128\)
\(2^x=32=2^5\Rightarrow x=5\)
a, 4x3 + 15 = 47
<=> 4x3 = 32
<=> x3 = 8
<=> x = 2
b, 4.2x - 3 = 125
<=> 4.2x = 128
<=> 2x = 32
<=> 2x = 25
<=> x = 5
a) 4.x3 + 15 = 47
=> 4.x3 = 47 - 15 = 32
=> x3 = 32:4 = 8
=> x3 = 23
=> x= 2
b) 4.2x - 3 = 125
=> 4.2x = 125 + 3 =128
=> 2x = 128 : 4 = 32
=> 2x = 25
=> x = 5
a) 4x3 + 15 = 47
4x3 = 47 - 15
4x3 = 32
x3 = 32 : 4
x3 = 8
=> x = 2
b)4.2x - 3 = 125
4.2x = 125 + 3
4.2x = 128
2x = 128 : 4
2x = 32
=> x = 5
\(4x^3+15=47\)
\(4x^3=32\)
\(x^3=8\)
\(x^3=2^3\)
\(\Rightarrow x=2\)
\(4.2^x-3=125\)
\(4.2^x=128\)
\(2^x=32\)
\(2^x=2^5\)
\(\Rightarrow x=5\)
a)\(4x^3+15=47\)
\(4x^3=47-15\)
\(4x^3=32\)
\(x^3=8\)
\(x^3=2^3\)
\(\Rightarrow x=2\)
Vậy \(x=2\)
b)\(4\cdot2^x-3=125\)
\(4\cdot2^x=125+3\)
\(4\cdot2^x=128\)
\(2^x=32\)
\(2^x=2^5\)
\(\Rightarrow x=5\)
Vậy\(x=5\)
\(\text{Tìm số tự nhiên }x\text{ biết : }\)
\(a,\text{ }4x^3+15=47\)
\(4x^3=47-15\)
\(4x^3=32\)
\(x^3=32\text{ : }4\)
\(x^3=8=2^3\)
\(\Rightarrow\text{ }x=2\)
\(b,\text{ }4\cdot2^x-3=125\)
\(4\cdot2^x=125+3\)
\(4\cdot2^x=128\)
\(2^x=128\text{ : }4\)
\(2^x=32=2^5\)
\(\Rightarrow\text{ }x=5\)
