Bài 2 :
a) \(3^4.3^x=3^7\)
\(\Rightarrow3^x=3^7:3^4\)
\(\Rightarrow3^x=3^3\)
\(\Rightarrow x=3\)
b) \(\left(2x+1\right)^3=125\)
\(\Rightarrow\left(2x+1\right)^3=5^3\)
\(\Rightarrow2x+1=5\)
\(\Rightarrow2x=4\)
\(\Rightarrow x=2\)
c) \(5^x.5^{x+1}.5^{x+2}=5^{25}:5^7\)
\(\Rightarrow5^{x+x+1+x+2}=5^{25-7}\)
\(\Rightarrow5^{3x+3}=5^{18}\)
\(\Rightarrow3x+3=18\)
\(\Rightarrow3x=15\)
\(\Rightarrow x=5\)
Bài 3 :
\(A=1+2^1+2^2+2^3+...+2^{2021}\)
\(\Rightarrow A=\dfrac{2^{2021+1}-1}{2-1}\)
\(\Rightarrow A=2^{2022}-1\)
Đúng 1
Bình luận (0)
