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câu cuối cùng pt cho thành mũ 2

1. ĐKXĐ: $\xgeq \frac{-6}{5}$

PT \(\Leftrightarrow [\sqrt{2x^2+5x+7}-(x+3)]+[(x+2)-\sqrt{5x+6}]+(x^2-x-2)=0\)

\(\Leftrightarrow \frac{x^2-x-2}{\sqrt{2x^2+5x+7}+x+3}+\frac{x^2-x-2}{x+2+\sqrt{5x+6}}+(x^2-x-2)=0\)

\(\Leftrightarrow (x^2-x-2)\left(\frac{1}{\sqrt{2x^2+5x+7}+x+3}+\frac{1}{x+2+\sqrt{5x+6}}+1\right)=0\)

Với $x\geq \frac{-6}{5}$, dễ thấy biểu thức trong ngoặc lớn hơn hơn $0$

Do đó: $x^2-x-2=0$

$\Leftrightarrow (x+1)(x-2)=0$

$\Leftrightarrow x=-1$ hoặc $x=2$ (đều thỏa mãn)

Bài 2: Tham khảo tại đây:

Giải pt \(\sqrt{2x+1} - \sqrt[3]{x+4} = 2x^2 -5x -11\) - Hoc24

7/

ĐKXĐ: \(-3\le x\le\frac{2}{3}\)

\(\Leftrightarrow2x+8\sqrt{x+3}+4\sqrt{3-2x}=2\)

\(\Leftrightarrow8\sqrt{x+3}+4\sqrt{3-2x}-\left(3-2x\right)+1=0\)

\(\Leftrightarrow8\sqrt{x+3}+\sqrt{3-2x}\left(4-\sqrt{3-2x}\right)+1=0\)

Do \(x\ge-3\Rightarrow3-2x\le9\Rightarrow\sqrt{3-2x}\le3\)

\(\Rightarrow4-\sqrt{3-2x}>0\)

\(\Rightarrow VT>0\)

Phương trình vô nghiệm (bạn coi lại đề)

5/

\(\Leftrightarrow8x^2-3x+6-4x\sqrt{3x^2+x+2}=0\)

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

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

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

6/

ĐKXĐ: ....

\(\Leftrightarrow\left(x-2000-2\sqrt{x-2000}+1\right)+\left(y-2001-2\sqrt{y-2001}+1\right)+\left(z-2002-2\sqrt{z-2002}+1\right)=0\)

\(\Leftrightarrow\left(\sqrt{x-2000}-1\right)^2+\left(\sqrt{y-2001}-1\right)^2+\left(\sqrt{z-2002}-1\right)^2=0\)

\(\Leftrightarrow\left\{{}\begin{matrix}\sqrt{x-2000}-1=0\\\sqrt{y-2001}-1=0\\\sqrt{z-2002}-1=0\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}x=2001\\y=2002\\z=2003\end{matrix}\right.\)

7.

ĐKXĐ: ...

\(\Leftrightarrow10\sqrt{\left(x+1\right)\left(x^2-x+1\right)}=3\left(x^2+2\right)\)

Đặt \(\left\{{}\begin{matrix}\sqrt{x^2-x+1}=a>0\\\sqrt{x+1}=b\ge0\end{matrix}\right.\)

\(\Rightarrow10ab=3\left(a^2+b^2\right)\)

\(\Leftrightarrow3a^2-10ab+3b^2=0\)

\(\Leftrightarrow\left(a-3b\right)\left(3b-a\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}a=3b\\3a=b\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}\sqrt{x^2-x+1}=3\sqrt{x+1}\\3\sqrt{x^2-x+1}=\sqrt{x-1}\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x^2-x+1=9x+9\\9x^2-9x+9=x-1\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x^2-10x-8=0\\9x^2-10x+10=0\end{matrix}\right.\) (casio)

6.

ĐKXĐ: ...

\(\Leftrightarrow2x^2+4=3\sqrt{\left(x+1\right)\left(x^2-x+1\right)}\)

Đặt \(\left\{{}\begin{matrix}\sqrt{x^2-x+1}=a>0\\\sqrt{x+1}=b\ge0\end{matrix}\right.\)

\(\Rightarrow2a^2+2b^2=3ab\)

\(\Leftrightarrow2a^2-3ab+2b^2=0\)

Phương trình vô nghiệm (vế phải là \(5\sqrt{x^3+1}\) sẽ hợp lý hơn)

c: =>3x^2+3y^2=39 và 3x^2-2y^2=-6

=>5y^2=45 và x^2=13-y^2

=>y^2=9 và x^2=4

=>\(\left\{{}\begin{matrix}x\in\left\{2;-2\right\}\\y\in\left\{3;-3\right\}\end{matrix}\right.\)

d: \(\Leftrightarrow\left\{{}\begin{matrix}5\sqrt{x}=5\\\sqrt{x}-\sqrt{y}=-\dfrac{11}{2}\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=1\\\sqrt{y}=1+\dfrac{11}{2}=\dfrac{13}{2}\end{matrix}\right.\)

=>x=1 và y=169/4

b: \(\Leftrightarrow\left\{{}\begin{matrix}\dfrac{3x+3-3}{x+1}-\dfrac{2}{y+4}=4\\\dfrac{2x+2-2}{x+1}-\dfrac{5}{y+4}=9\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}-\dfrac{3}{x+1}-\dfrac{2}{y+4}=4-3=1\\-\dfrac{2}{x+1}-\dfrac{5}{y+4}=9-2=7\end{matrix}\right.\)

=>x+1=11/9 và y+4=-11/19

=>x=2/9 và y=-87/19

c, ĐKXĐ: \(x\ge\frac{1}{2}\)

\(\sqrt{x-\sqrt{2x-1}}=\sqrt{2}\)

\(\Leftrightarrow\sqrt{2x-2\sqrt{2x-1}}=2\)

\(\Leftrightarrow\sqrt{2x-1-2\sqrt{2x-1}+1}=2\)

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

\(\Leftrightarrow\left|\sqrt{2x-1}-1\right|=2\)

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

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

\(\sqrt{2x-1}=3\Leftrightarrow2x-1=9\Leftrightarrow x=5\left(tm\right)\)

a, ĐKXĐ: \(x\in R\)

\(\sqrt{3x^2}=x+2\)

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

TH1: \(\sqrt{3}x=x+2\)

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

\(\Leftrightarrow x=\sqrt{3}+1\)

TH2: \(\sqrt{3}x=-x-2\)

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

\(\Leftrightarrow x=1-\sqrt{3}\)

mọi người giúp mình với ạ,mai mình phải nộp rồi nhưng kô biết làm .Mong mn giúp đỡ!!!

Bài dễ mà :
a, \(\sqrt{x+5}=x+15 \)
\(x+5=x^2+30x+225\)
\(x^2+29x+220=0\)
\(\left(x+14,5\right)^2+9,75=0\)
pt vô nghiệm

1) Đk: x khác -3

x khác 1

Biểu thức \(\Leftrightarrow\dfrac{x^2-x}{x^2+2x-3}+\dfrac{2x+6}{x^2+2x-3}=\dfrac{12}{x^2+2x-3}\)

\(\Leftrightarrow x^2-x+2x+6=12\Leftrightarrow x^2+x-6=0\Leftrightarrow\left(x-2\right)\left(x+3\right)=0\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-3\end{matrix}\right.\)

kl: x thuộc {-3;2}

@Nguyễn Thị Giang Thanh

6.

Đặt \(\left\{{}\begin{matrix}\sqrt{5x^2+6x+5}=a\\4x=b\end{matrix}\right.\)

\(\Rightarrow a\left(a^2+1\right)=b\left(b^2+1\right)\)

\(\Leftrightarrow a^3-b^3+a-b=0\)

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

\(\Leftrightarrow a=b\)

\(\Leftrightarrow\sqrt{5x^2+6x+5}=4x\left(x\ge0\right)\)

\(\Leftrightarrow5x^2+6x+5=16x^2\)

\(\Leftrightarrow11x^2-6x-5=0\)

\(\Rightarrow x=1\)

4. Bạn coi lại đề (chính xác là pt này ko có nghiệm thực)

5.

\(\Leftrightarrow x^2+x+6-\left(2x+1\right)\sqrt{x^2+x+6}+6x-6=0\)

Đặt \(\sqrt{x^2+x+6}=t>0\)

\(t^2-\left(2x+1\right)t+6x-6=0\)

\(\Delta=\left(2x+1\right)^2-4\left(6x-6\right)=\left(2x-5\right)^2\)

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

\(\Leftrightarrow\left[{}\begin{matrix}\sqrt{x^2+x+6}=2x-2\left(x\ge1\right)\\\sqrt{x^2+x+6}=3\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x^2+x+6=4x^2-8x+4\left(x\ge1\right)\\x^2+x+6=9\end{matrix}\right.\)