Question

LAMF BẰNG PP CHẶN GIÚP MIK Ạ

MIK CẢM ƠN Ạ

Answer 1

\(3.A=\dfrac{2\sqrt{x}+17}{\sqrt{x}+5}=\dfrac{2\left(\sqrt{x}+5\right)+7}{\sqrt{x}+5}\)\(=2+\dfrac{7}{\sqrt{x}+5}\)

\(\sqrt{x}+5\ge5=>2+\dfrac{7}{\sqrt{x}+5}\le2+\dfrac{7}{5}=3,4\)

dấu'=' xảy ra<=>x=0=>MaxA=3,4

Answer 2

3.\(A=\dfrac{2\sqrt{x}+17}{\sqrt{x}+5}=2+\dfrac{7}{\sqrt{x}+5}\)

\(A\in Z< =>\sqrt{x}+5\inƯ\left(7\right)=\left\{\pm1;\pm7\right\}\)

\(=>x\in\left\{4\right\}\)