Question

A=\(-\dfrac{1}{\sqrt{x}+1}\)

a) Tìm x để A=\(\dfrac{1}{2}\)

b) Tính A khi x=9+√32

c) Tìm x để A>0

d) Tìm x∈Z

để A∈Z

e) Tìm x để A Min

Answer 1

\(A=-\dfrac{1}{\sqrt{x}+1}\)

\(a,\) Để A = \(\dfrac{1}{2}\)

\(\Rightarrow-\dfrac{1}{\sqrt{2}+1}=\dfrac{1}{2}\)

\(\Rightarrow\sqrt{x}+1=2\)

\(\Rightarrow\sqrt{x}=1\)

\(\Rightarrow x=1\)

b,Với \(x=9+\sqrt{32}\)

\(\Rightarrow A=-\dfrac{1}{9+\sqrt{32}+1}\)

\(\Rightarrow A=\dfrac{-5+2\sqrt{2}}{34}\)

VậY\(A=\dfrac{-5+2\sqrt{2}}{34}\)

Answer 2

\(A=-\dfrac{1}{\sqrt{x}+1}\\ \dfrac{1}{2}=-\dfrac{1}{\sqrt{x}+1}\\ \sqrt{x}+1=-2\\ \sqrt{x}=-3\\ x=-9\)

Answer 3

mk tính sai nha bn