Question

Tinh:

a/\(\frac{10^3+2.5^3+5^3}{55}\)

b/\(2^x+2^{x+3}=144\) 

c/\(2\left(x-5\right)+3\left(x-7\right)=10\)

Answer 1

a)\(\frac{10^3+2.5^3+5^3}{55}\)=\(\frac{5^3.2^3+2.5^3+5^3}{5.11}\)=\(\frac{5^3.\left(2^3+2+1\right)}{5.11}\)=\(5^2\)=\(25\)

b) \(2^x+2^{x+3}=144\)

\(\Rightarrow2^x+2^x.2^3=144\)

\(\Rightarrow2^x.\left(1+2^3\right)=144\)

\(\Rightarrow2^x=16=2^4\)

\(\Rightarrow x=4\)

c) \(2\left(x-5\right)+3\left(x-7\right)=10\)

\(\Rightarrow2x-10+3x-21=10\)

\(\Rightarrow5x-31=10\)

\(\Rightarrow5x=41\)

\(\Rightarrow x=\frac{41}{5}=8,2\)