Question

P=3/(căn x+1) c) tìm các giá trị của x để 1/P=4/5

Answer 1

c) Ta có: \(\dfrac{1}{P}=\dfrac{4}{5}\)

\(\Rightarrow1:\left(\dfrac{3}{\sqrt{x}+1}\right)=\dfrac{4}{5}\)

\(\Leftrightarrow\dfrac{3}{\sqrt{x}+1}=\dfrac{5}{4}\)

\(\Leftrightarrow5\left(\sqrt{x}+1\right)=12\)

\(\Leftrightarrow\sqrt{x}-1=\dfrac{12}{5}\)

\(\Leftrightarrow\sqrt{x}=\dfrac{12}{5}+1\)

\(\Leftrightarrow\sqrt{x}=\dfrac{17}{5}\)

\(\Leftrightarrow x=\left(\dfrac{17}{5}\right)^2=\dfrac{289}{25}\)

Answer 2

Sửa đề : (xem lại)

`c)1/P=4/3`

`=>P=3/4`

`<=>3/(\sqrtx+1)=3/4`

`=>\sqrtx+1=4`

`=>\sqrtx=3`

`=>x=9(t/m)` 

Vậy với `x=9` thì `1/P=4/3`