Hummmm

Dạ em không biết ạ,tại vì em mới học lớp 4 ạ,em xin lỗi ạ

a, ĐKXĐ : \(\left[{}\begin{matrix}x\le-3\\x\ge0\end{matrix}\right.\)

TH1 : \(x\le-3\) ( LĐ )

TH2 : \(x\ge0\)

BPT \(\Leftrightarrow x^2+2x+x^2+3x+2\sqrt{\left(x^2+2x\right)\left(x^2+3x\right)}\ge4x^2\)

\(\Leftrightarrow\sqrt{\left(x^2+2x\right)\left(x^2+3x\right)}\ge x^2-\dfrac{5}{2}x\)

\(\Leftrightarrow2\sqrt{\left(x+2\right)\left(x+3\right)}\ge2x-5\)

\(\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x< \dfrac{5}{2}\\x\ge-2\end{matrix}\right.\\\left\{{}\begin{matrix}x\ge\dfrac{5}{2}\\4x^2+20x+24\ge4x^2-20x+25\end{matrix}\right.\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}0\le x< \dfrac{5}{2}\\x\ge\dfrac{5}{2}\end{matrix}\right.\)

\(\Leftrightarrow x\ge0\)

Vậy \(S=R/\left(-3;0\right)\)

1) \(\sqrt[]{3x+7}-5< 0\)

\(\Leftrightarrow\sqrt[]{3x+7}< 5\)

\(\Leftrightarrow3x+7\ge0\cap3x+7< 25\)

\(\Leftrightarrow x\ge-\dfrac{7}{3}\cap x< 6\)

\(\Leftrightarrow-\dfrac{7}{3}\le x< 6\)

Em 2k8 k biết làm có đúng k

ĐKXĐ : \(\left[{}\begin{matrix}x\le-1\\x\ge3\end{matrix}\right.\) 

Bpt \(\Leftrightarrow\left(x-2\right)\left[x+2-\sqrt{x^2-2x-3}\right]\ge0\)

\(\Leftrightarrow\left[{}\begin{matrix}x\ge2;x+2\ge\sqrt{x^2-2x-3}\left(1\right)\\x\le2;x+2\le\sqrt{x^2-2x-3}\left(2\right)\end{matrix}\right.\)

(1) có :  \(x+2\ge\sqrt{x^2-2x-3}\Leftrightarrow\left(x+2\right)^2\ge x^2-2x-3\)

\(\Leftrightarrow6x+7\ge0\)  (Đ với \(x\ge2\) )

(2) có : \(\sqrt{x^2-2x-3}\ge x+2\)

TH1 : x + 2 < 0 <=> \(x< -2\)  ( Bpt luôn đúng ) 

TH2 : \(x+2\ge0\) ; Bp 2 vế rút gọn được : \(6x+7\le0\Leftrightarrow x\le\dfrac{-7}{6}\)

Khi đó : \(-2\le x\le\dfrac{-7}{6}\)

Vậy ... 

\(\sqrt[3]{2x^2+1}>\sqrt[3]{3x^2-1}\)

\(\Leftrightarrow2x^2+1>3x^2-1\)

\(\Leftrightarrow x^2< 2\)

\(\Leftrightarrow-\sqrt{2}< x< \sqrt{2}\)