Question

cho f(x)=\(\frac{x+2}{x-1}\)

a)tinh f(7)

b)tim x de f(x)=\(\frac{1}{4}\)

c)tim x de f(x)>1

Answer 1

\(f\left(7\right)=\frac{7+2}{7-1}=\frac{9}{6}=\frac{3}{2}\)

b)

\(f\left(x\right)=\frac{1}{4}\Rightarrow\frac{\left(x+2\right)}{x-1}=\frac{1}{4}\)

dk \(x\ne1\Leftrightarrow4.\left(x+2\right)=x-1\Leftrightarrow4x+8=x-1\Rightarrow x=-3\)

c)

\(f\left(x\right)>1=>\frac{x+2}{x-1}>1\Leftrightarrow\frac{\left(x+2\right)-\left(x-1\right)}{x-1}>0\)

\(\Leftrightarrow\frac{3}{x-1}>0\Leftrightarrow x-1>0\Rightarrow x>1\)