Tìm x:
a,\(\frac{x+1}{2}=\frac{8}{x+1}\) b,\(x:\left(9\frac{1}{2}-\frac{3}{2}\right)=\frac{0,4+\frac{2}{9}-\frac{2}{11}}{1,6+\frac{8}{9}-\frac{8}{11}}\)
c, x + (x + 1) + (x + 2) +...+ (x + 30)=1240 d) \(\frac{5}{1.6}+\frac{5}{6.11}+...+\frac{5}{\left(5x\right)+1\left(5x\right)+6}=\frac{2005}{2006}\)
a,\(\frac{x+1}{2}\)\(=\frac{8}{x+1}\)
\(\Leftrightarrow\)(x+1)\(\times\)(x+1) = 8 \(\times\)2
\(\Leftrightarrow\)(x+1)2 = 16
\(\Leftrightarrow\)(x+1)2 = 42
\(\Rightarrow\)x+1 = 4
\(\Rightarrow\)x = 4 - 1
\(\leftrightarrow\)x = 3