Hung nguyen, Trần Thanh Phương, Sky SơnTùng, @tth_new, @Nguyễn Việt Lâm, @Akai Haruma, @No choice teen

help me, pleaseee

Cần gấp lắm ạ!

a: Ta có: \(\sqrt{4x+20}-3\sqrt{x+5}+\dfrac{4}{3}\sqrt{9x+45}=6\)

\(\Leftrightarrow2\sqrt{x+5}-3\sqrt{x+5}+4\sqrt{x+5}=6\)

\(\Leftrightarrow3\sqrt{x+5}=6\)

\(\Leftrightarrow x+5=4\)

hay x=-1

b: Ta có: \(\dfrac{1}{2}\sqrt{x-1}-\dfrac{3}{2}\sqrt{9x-9}+24\sqrt{\dfrac{x-1}{64}}=-17\)

\(\Leftrightarrow\dfrac{1}{2}\sqrt{x-1}-\dfrac{9}{2}\sqrt{x-1}+3\sqrt{x-1}=-17\)

\(\Leftrightarrow\sqrt{x-1}=17\)

\(\Leftrightarrow x-1=289\)

hay x=290

\(\sqrt{x-2}+\sqrt{4-x}=2x^2-5x-1\)

\(\Leftrightarrow\sqrt{x-2}-1+\sqrt{4-x}-1=2x^2-5x-3\)

\(\Leftrightarrow\left(x-3\right)\left(\frac{1}{\sqrt{x-2}+1}+\frac{1}{\sqrt{4-x}+1}+2x+1\right)=0\)

\(\Rightarrow x=3\)

phương trình còn lại mk chưa giải đc nhưng nó vô nghiệm

Em thử câu c nha, sai thì thôi

c) ĐK: \(x\ge-1\).Nhận xét x = 0 là không phải nghiệm, xét x khác 0:

Nhân liên hợp ta được \(\left(x+4\right).\left(\frac{x}{\sqrt{x+1}-1}\right)^2=x^2\)

\(\Leftrightarrow\frac{x+4}{\left(\sqrt{x+1}-1\right)^2}=1\Leftrightarrow x+4=\left(\sqrt{x+1}-1\right)^2\)

\(\Leftrightarrow x+4=x+2-2\sqrt{x+1}\) (rút gọn vế phải)

\(\Leftrightarrow\sqrt{x+1}=-1\left(\text{vô lí}\right)\)

Vậy pt vô nghiệm

\(d,pt\Leftrightarrow\sqrt{2x^2+5x+7}-5-\sqrt{5x+6}+4+x^2-x-2=0\)

\(\Leftrightarrow\left(x-2\right)\left(\frac{2x+9}{\sqrt{2x^2+5x+7}+5}+\frac{5}{4+\sqrt{5x+6}}+x+1\right)=0\)

\(\Leftrightarrow x=2\)

hihi mk chỉ bít làm đến đây thui có j các bạn giải nốt giúp mk vs nhá

^.^

Liên hợp:v

a) ĐK: \(x\ge-2\)

PT<=> \(\sqrt{x+5}-2+\sqrt{x+2}-1+2\left(x+1\right)=0\)

\(\Leftrightarrow\frac{x+1}{\sqrt{x+5}+2}+\frac{x+1}{\sqrt{x+2}+1}+2\left(x+1\right)=0\)

\(\Leftrightarrow\left(x+1\right)\left(\frac{1}{\sqrt{x+5}+2}+\frac{1}{\sqrt{x+2}+1}+2\right)=0\)

Cái ngoặc to nhìn sơ qua cũng thấy nó >0 :v

Do đó x = -1

Vậy...

P/s: cô @Akai Haruma check giúp em ạ!

Nguyễn Việt Lâm, svtkvtm, Trần Thanh Phương, Phạm Hoàng Hải Anh, DƯƠNG PHAN KHÁNH DƯƠNG, @Akai Haruma

1/ Đặt \(\sqrt[3]{x^2+5x-2}=t\Rightarrow x^2+5x=t^3+2\)

\(t^3+2=2t-2\)

\(\Leftrightarrow t^3-2t+4=0\)

\(\Leftrightarrow\left(t+2\right)\left(t^2-2t+2\right)=0\)

\(\Rightarrow t=-2\)

\(\Rightarrow\sqrt[3]{x^2+5x-2}=-2\)

\(\Leftrightarrow x^2+5x-2=-8\)

\(\Leftrightarrow x^2+5x+6=0\Rightarrow\left[{}\begin{matrix}x=-2\\x=-3\end{matrix}\right.\)

2/ \(\Leftrightarrow2x+11+3\sqrt[3]{\left(x+5\right)\left(x+6\right)}\left(\sqrt[3]{x+5}+\sqrt[3]{x+6}\right)=2x+11\)

\(\Leftrightarrow\sqrt[3]{\left(x+5\right)\left(x+6\right)}\left(\sqrt[3]{x+5}+\sqrt[3]{x+6}\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}\sqrt[3]{x+5}=0\\\sqrt[3]{x+6}=0\\\sqrt[3]{x+5}=-\sqrt[3]{x+6}\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=-5\\x=-6\\x+5=-x-6\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x=-5\\x=-6\\x=-\frac{11}{2}\end{matrix}\right.\)

3/ ĐKXĐ: \(\left|x\right|\ge1\)

Đặt \(\left\{{}\begin{matrix}\sqrt[4]{x-\sqrt{x^2-1}}=a>0\\\sqrt[4]{x+\sqrt{x^2-1}}=b>0\end{matrix}\right.\) ta được:

\(\left\{{}\begin{matrix}ab=1\\a+b^2=2\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}ab=1\\a=2-b^2\end{matrix}\right.\)

\(\Rightarrow b\left(2-b^2\right)=1\Leftrightarrow b^3-2b+1=0\)

\(\Leftrightarrow\left(b-1\right)\left(b^2+b-1\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}b=1\\b^2+b-1=0\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}b=1\\b=\frac{-1+\sqrt{5}}{2}\\b=\frac{-1-\sqrt{5}}{2}\left(l\right)\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}\sqrt[4]{x+\sqrt{x^2-1}}=1\\\sqrt[4]{x+\sqrt{x^2-1}}=\frac{-1+\sqrt{5}}{2}\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x+\sqrt{x^2-1}=1\\x+\sqrt{x^2-1}=\frac{7-3\sqrt{5}}{2}\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=1\\\sqrt{x^2-1}=\frac{7-3\sqrt{5}}{2}-x\left(vn\right)\end{matrix}\right.\)

Câu 2,3,4 nx thôi ạ. Câu 1 có bạn giúp r ạ 

1)\(\sqrt{4x^2+12x+9}=2-x\)

\(\Leftrightarrow\sqrt{\left(2x+3\right)^2}=2-x\)

\(\Leftrightarrow\left|2x+3\right|=2-x\)

\(\Leftrightarrow\left[{}\begin{matrix}2x+3=2-x\\2x+3=x-2\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}3x=-1\\x=-5\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{1}{3}\\x=-5\end{matrix}\right.\)

\(\)

2)\(\sqrt{x^4+2x^2+1}=x^2+5x+4\)       ĐK:\(x\ge-1\)

\(\Leftrightarrow\sqrt{\left(x^2+1\right)^2}=x^2+5x+4\)

\(\Leftrightarrow\left|x^2+1\right|=x^2+5x+4\)

\(\Leftrightarrow\left[{}\begin{matrix}x^2+1=x^2+5x+4\\x^2+1=-x^2-5x-4\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}5x=-3\\2x^2+5x+5=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{3}{5}\\2\left(x+\dfrac{5}{4}\right)^2+\dfrac{15}{8}=0\left(voli\right)\end{matrix}\right.\)