\(\sqrt{2x^2-16x+41}+\sqrt{3x^2-24x+64}=7\)

Ta đánh giá vế phải \(\sqrt{2x^2-16x+41}+\sqrt{3x^2-24x+64}=\sqrt{2\left(x-4\right)^2+9}+\sqrt{3\left(x-4\right)^2+16}\ge\sqrt{9}+\sqrt{16}=3+4=7\)(Do \(\left(x-4\right)^2\ge0\forall x\))

Như vậy, để \(\sqrt{2x^2-16x+41}+\sqrt{3x^2-24x+64}=7\)(hay dấu "=" xảy ra) thì \(\left(x-4\right)^2=0\)hay x = 4

Vậy nghiệm duy nhất của phương trình là 4

f, \(\sqrt{8+\sqrt{x}}+\sqrt{5-\sqrt{x}}=5\left(đk:25\ge x\ge0\right)\)

\(< =>\sqrt{8+\sqrt{x}}-\sqrt{9}+\sqrt{5-\sqrt{x}}-\sqrt{4}=0\)

\(< =>\frac{8+\sqrt{x}-9}{\sqrt{8+\sqrt{x}}+\sqrt{9}}+\frac{5-\sqrt{x}-4}{\sqrt{5-\sqrt{x}}+\sqrt{4}}=0\)

\(< =>\frac{\sqrt{x}-1}{\sqrt{8+\sqrt{x}}+\sqrt{9}}-\frac{\sqrt{x}-1}{\sqrt{5-\sqrt{x}}+\sqrt{4}}=0\)

\(< =>\left(\sqrt{x}-1\right)\left(\frac{1}{\sqrt{8+\sqrt{x}}+\sqrt{9}}-\frac{1}{\sqrt{5-\sqrt{x}}+\sqrt{4}}\right)=0\)

\(< =>x=1\)( dùng đk đánh giá cái ngoặc to nhé vì nó vô nghiệm )

ĐKXĐ:...

f/ \(2\sqrt{x+5}-3\sqrt{x+5}+4\sqrt{x+5}=6\)

\(\Leftrightarrow3\sqrt{x+5}=6\Rightarrow\sqrt{x+5}=2\)

\(\Rightarrow x+5=4\Rightarrow x=-1\)

g/ \(3\left|x-1\right|=15\)

\(\Rightarrow\left|x-1\right|=5\)

\(\Rightarrow\left[{}\begin{matrix}x-1=5\\x-1=-5\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x=6\\x=-4\end{matrix}\right.\)

i/ \(3x-7+\sqrt{3x-7}=0\)

\(\Leftrightarrow\sqrt{3x-7}\left(\sqrt{3x-7}+1\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}\sqrt{3x-7}=0\\\sqrt{3x-7}=-1\left(vn\right)\end{matrix}\right.\) \(\Rightarrow x=\frac{7}{3}\)

k/ \(\sqrt{2x+5}=x+3\) (\(x\ge-3\))

\(\Leftrightarrow2x+5=\left(x+3\right)^2\)

\(\Leftrightarrow x^2+4x+4=0\)

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

a) \(\left|3x+1\right|=\left|x+1\right|\)

\(\Leftrightarrow\left[{}\begin{matrix}3x+1=x+1\\3x+1=-x-1\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-\dfrac{1}{2}\end{matrix}\right.\)

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

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

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

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

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

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

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

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

e) \(\left|x^2-1\right|+\left|x+1\right|=0\)

\(\Leftrightarrow\left\{{}\begin{matrix}x^2-1=0\\x+1=0\end{matrix}\right.\)

\(\Leftrightarrow x=-1\)

f) \(\sqrt{x^2-8x+16}+\left|x+2\right|=0\)

\(\Leftrightarrow\sqrt{\left(x-4\right)^2}+\left|x+2\right|=0\)

\(\Leftrightarrow\left|x-4\right|+\left|x+2\right|=0\)

⇒ vô nghiệm

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

help me, pleaseee

Cần gấp lắm ạ!

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

\(\Leftrightarrow4-\left(1-x\right)^2=3\)

\(\Leftrightarrow4-\left(1-2x+x^2\right)-3=0\)

\(\Leftrightarrow4-1+2x-x^2-3=0\)

\(\Leftrightarrow-x\left(x-2\right)=0\Leftrightarrow\orbr{\begin{cases}x=0\\x-2=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=0\\x=2\end{cases}}}\)

vay x=0 ; x=2

\(\sqrt{3x^2-5=2}\left(x\ge\sqrt{\frac{5}{3}}\right)\)

\(\Leftrightarrow3x^2-5=4\)

\(\Leftrightarrow3x^2=9\Leftrightarrow x^2=3\Leftrightarrow\orbr{\begin{cases}x=\sqrt{3}\left(tm\right)\\x=-\sqrt{3}\left(kotm\right)\end{cases}}\)

vay \(x=\sqrt{3}\)

\(\sqrt{\left(\sqrt{x}-7\right)\left(\sqrt{x}+7\right)}=2\left(x\ge49\right)\)

\(\Leftrightarrow\sqrt{x-49}=2\Leftrightarrow x^2-98x+2401=4\)

\(\Leftrightarrow x^2-98x+2397=0\Leftrightarrow x^2-47x-51x+2397\)\(\Leftrightarrow x\left(x-47\right)-51\left(x-47\right)\Leftrightarrow\left(x-47\right)\left(x-51\right)\)

\(\Leftrightarrow\orbr{\begin{cases}x-51=0\\x-47=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=51\left(tm\right)\\x=47\left(kotm\right)\end{cases}}}\)

xay x=51

\(\sqrt{\frac{-6}{1+x}}=5\left(x< -1\right)\)

\(\Leftrightarrow\frac{36}{x^2+2x+1}=25\Leftrightarrow25x^2+50x+25=36\)

\(\Leftrightarrow25x^2+50x-11=0\Leftrightarrow25x^2-5x+55x-11\)

\(\Leftrightarrow5x\left(5x-1\right)+11\left(5x-1\right)\Leftrightarrow\left(5x-1\right)\left(5x+11\right)\)\(\Leftrightarrow\orbr{\begin{cases}5x-1=0\\5x+11=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=\frac{1}{5}\left(kotm\right)\\x=\frac{-11}{5}\left(tm\right)\end{cases}}}\)

vay \(x=\frac{-11}{5}\)

nhung cau nay binh phuong len la xong 

y 3 xem lai de bai 

y 4,7 ko biet lam

k) ĐK: $x^2\geq 5$

PT $\Leftrightarrow 2\sqrt{x^2-5}-\frac{1}{3}\sqrt{x^2-5}+\frac{3}{4}\sqrt{x^2-5}-\frac{5}{12}\sqrt{x^2-5}=4$

$\Leftrightarrow 2\sqrt{x^2-5}=4$

$\Leftrightarrow \sqrt{x^2-5}=2$

$\Rightarrow x^2-5=4$

$\Leftrightarrow x^2=9\Rightarrow x=\pm 3$ (đều thỏa mãn)

l) ĐKXĐ: $x\geq -1$

PT $\Leftrightarrow 2\sqrt{x+1}+3\sqrt{x+1}-\sqrt{x+1}=4$

$\Leftrightarrow 4\sqrt{x+1}=4$

$\Leftrightarrow \sqrt{x+1}=1$

$\Rightarrow x+1=1$

$\Rightarrow x=0$

m) 

ĐKXĐ: $x\geq -1$

PT $\Leftrightarrow 4\sqrt{x+1}+2\sqrt{x+1}=16-\sqrt{x+1}+3\sqrt{x+1}$

$\Leftrightarrow 6\sqrt{x+1}=16+2\sqrt{x+1}$

$\Leftrightarrow 4\sqrt{x+1}=16$

$\Leftrightarrow \sqrt{x+1}=4$

$\Rightarrow x=15$ (thỏa mãn)

h) 

ĐKXĐ: $x\geq -5$

PT $\Leftrightarrow \sqrt{x+5}=6$

$\Rightarrow x+5=36\Rightarrow x=31$ (thỏa mãn)

i) ĐKXĐ: $x\geq 5$

PT \(\Leftrightarrow \sqrt{x-5}+4\sqrt{x-5}-\sqrt{x-5}=12\)

\(\Leftrightarrow 4\sqrt{x-5}=12\Leftrightarrow \sqrt{x-5}=3\Rightarrow x-5=9\Rightarrow x=14\) (thỏa mãn)

j) 

ĐKXĐ: $x\geq 0$

PT $\Leftrightarrow 3\sqrt{2x}+\sqrt{2x}-6\sqrt{2x}+4=0$

$\Leftrightarrow -2\sqrt{2x}+4=0$

$\Leftrightarrow \sqrt{2x}=2$

$\Rightarrow x=2$ (thỏa mãn)

a)

ĐKXĐ: \(x> \frac{-5}{7}\)

Ta có: \(\frac{9x-7}{\sqrt{7x+5}}=\sqrt{7x+5}\)

\(\Rightarrow 9x-7=\sqrt{7x+5}.\sqrt{7x+5}=7x+5\)

\(\Rightarrow 2x=12\Rightarrow x=6\) (hoàn toàn thỏa mãn)

Vậy......

b) ĐKXĐ: \(x\geq 5\)

\(\sqrt{4x-20}+3\sqrt{\frac{x-5}{9}}-\frac{1}{3}\sqrt{9x-45}=4\)

\(\Leftrightarrow \sqrt{4}.\sqrt{x-5}+3\sqrt{\frac{1}{9}}.\sqrt{x-5}-\frac{1}{3}\sqrt{9}.\sqrt{x-5}=4\)

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

\(\Leftrightarrow 2\sqrt{x-5}=4\Rightarrow \sqrt{x-5}=2\Rightarrow x-5=2^2=4\Rightarrow x=9\)

(hoàn toàn thỏa mãn)

Vậy..........

c) ĐK: \(x\in \mathbb{R}\)

Đặt \(\sqrt{6x^2-12x+7}=a(a\geq 0)\Rightarrow 6x^2-12x+7=a^2\)

\(\Rightarrow 6(x^2-2x)=a^2-7\Rightarrow x^2-2x=\frac{a^2-7}{6}\)

Khi đó:

\(2x-x^2+\sqrt{6x^2-12x+7}=0\)

\(\Leftrightarrow \frac{7-a^2}{6}+a=0\)

\(\Leftrightarrow 7-a^2+6a=0\)

\(\Leftrightarrow -a(a+1)+7(a+1)=0\Leftrightarrow (a+1)(7-a)=0\)

\(\Rightarrow \left[\begin{matrix} a=-1\\ a=7\end{matrix}\right.\) \(\Rightarrow a=7\) vì \(a\geq 0\)

\(\Rightarrow 6x^2-12x+7=a^2=49\)

\(\Rightarrow 6x^2-12x-42=0\Leftrightarrow x^2-2x-7=0\)

\(\Leftrightarrow (x-1)^2=8\Rightarrow x=1\pm 2\sqrt{2}\)

(đều thỏa mãn)

Vậy..........