\(2^x+2^{x+3}=288\)
\(\Rightarrow2^x+2^x.2^3=288\)
\(\Rightarrow2^x\left(1+2^3\right)=288\)
\(\Rightarrow2^x.9=288\)
\(\Rightarrow2^x=288:9\)
\(\Rightarrow2^x=32\)
\(\Rightarrow2^x=2^5\)
\(\Rightarrow x=5\)
Vậy \(x=5\)
\(x+\left(x+1\right)+\left(x+2\right)+\left(x+3\right)+...+\left(x+30\right)=1240\)
\(\Rightarrow x+x+1+x+2+x+3+...+x+30=1240\)
\(\Rightarrow x+x+x+...+x+1+2+3+...+30=1240\)
Từ \(1\rightarrow30\)có: \(\left(30-1\right):1+1=30\)( số )
\(\Rightarrow31.x+\left(30+1\right).30:2=1240\)
\(\Rightarrow31.x+31.15=1240\)
\(\Rightarrow31.x+465=1240\)
\(\Rightarrow31.x=1240-465\)
\(\Rightarrow31.x=775\)
\(\Rightarrow x=775:31\)
\(\Rightarrow x=25\)
Chúc bạn học tốt !!!
x+(x+1)+(x+2)+....+(x+30)=1240
31 . x + (1 + 2 + 3 + 4 +...+ 29 + 30) = 1240
31 . x + 31.15 = 1240
31 . x = 1240 - 31.15
31 . x = 775
x = 775 : 31
x = 25
Vậy x=25
\(x+\left(x+1\right)+\left(x+2\right)+\left(x+3\right)+...+\left(x+30\right)=1240\)
\(x+x+1+x+2+x+3+...+x+30=1240\)
\(31x+\left(1+2+3+...+30\right)=1240\)
ta xét \(1+2+3+...+30\)
số số hạng của dãy trên là
\(\left(30-1\right):1+1=30\)
tổng dãy trên là
\(\left(30+1\right).30:2=465\)
thay vào
\(31x+465=1240\)
\(31x=775\)
\(\Rightarrow x=25\)
