Question

Tìm số tự nhiên x, biết:

a) 3^x . 3 = 243

b) 2^x . 7 = 56

Giúp zới

Answer 1

a) \(3^x.3=243\)

\(\Rightarrow3^{x+1}=3^5\)

\(\Rightarrow x+1=5\)

\(\Rightarrow x=4\)

b) \(2^x.7=56\)

\(2^x=56:7\)

\(\Rightarrow2^x=8\)

\(\Rightarrow2^x=2^3\)

\(\Rightarrow x=3\)

Answer 2

\(3^x.3=243\)

\(\Rightarrow3^x=81\)

\(\Rightarrow3^x=3^4\)

\(\Rightarrow x=4\)

\(2^x.7=56\)

\(\Rightarrow2^x=56:7\)

\(\Rightarrow2^x=8\)

\(\Rightarrow2^x=2^3\)

\(\Rightarrow x=3\)

Answer 3

\(a,\)  \(3^x.3=243\)

\(\Rightarrow3^x.3=3^5\)

\(\Rightarrow3^x=3^5:3\)

\(\Rightarrow3^x=3^{5-1}\)

\(\Rightarrow3^x=3^4\)

\(\Rightarrow x=4\)

Vậy \(x=4\)

\(b,\) \(2^x.7=56\)

\(\Rightarrow2^x=56:7\)

\(\Rightarrow2^x=8\)

\(\Rightarrow2^x=2^3\)

\(\Rightarrow x=3\)

Vậy \(x=3\)

Answer 4

a) \(3^x.3=243\Leftrightarrow3^{x+1}=3^5\Rightarrow x+1=5\Leftrightarrow x=4\)

b) \(2^x.7=56\Leftrightarrow2^x=8\Leftrightarrow2^x=2^3\Leftrightarrow x=3\)

Answer 5

\(\Rightarrow3^x=\frac{243}{3}\)

\(\Rightarrow3^x=81\)

\(\Rightarrow3^x=\left(3\right)^4\)

\(\Rightarrow x=4\)

Answer 6

\(\Rightarrow2^x=\frac{56}{7}\)

\(\Rightarrow2^x=8\)

\(\Rightarrow2^x=2^3\)

\(\Rightarrow x=3\)

Answer 7

3^x . 3 = 243

3^x = 243 : 3

3^x = 81

3^x = 3⁴

x = 4

2^x . 7 = 56

2^x = 56 : 7

2^x = 8

2^x = 2³

x = 3

Answer 8

a)3^x.3=243

=>3^x=243:3

=>3^x=81

=>3^x=3⁴

=>x=4

b)2^x.7=56

=>2^x=56:7

=>2^x=8

=>2^x=2³

=>x=3