Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
Viết đề mà ko ai đọc được vậy :v
a) \(3x^2+2x+3=\left(3x+1\right)\sqrt{x^2+3}\)
\(\Leftrightarrow3x^2+2x+3-3x\sqrt{x^2+3}-\sqrt{x^2+3}=0\)
\(\Leftrightarrow x^2+3-x\sqrt{x^2+3}-\sqrt{x^2+3}-2x\sqrt{x^2+3}+2x^2+2x=0\)
\(\Leftrightarrow\sqrt{x^2+3}\cdot\left(\sqrt{x^2+3}-x-1\right)-2x\cdot\left(\sqrt{x^2+3}-x-1\right)=0\)
\(\Leftrightarrow\left(\sqrt{x^2+3}-x-1\right)\left(\sqrt{x^2+3}-2x\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}\sqrt{x^2+3}=x+1\left(x\ge-1\right)\\\sqrt{x^2+3}=2x\left(x\ge0\right)\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=1\\x=1\end{matrix}\right.\)\(\Leftrightarrow x=1\) ( thỏa mãn )
Vậy...
\(\left(4x-1\right)\sqrt{x^2+1}=2x^2+2x+1\) (1)
<=>\(\left(4x-1\right)\left[\sqrt{x^2+1}-\left(3-x\right)\right]=6x^2-11x+4\)
Xét \(\sqrt{x^2+1}+3-x=0\)
<=> \(x^2+1=x^2-6x+9\) <=>\(x=\frac{4}{3}\)(tm phương trình (1))
Xét \(\sqrt{x^2+1}+3-x\ne0\)
pt <=>\(\frac{\left(4x-1\right)\left(x^2+1-x^2+6x-9\right)}{\sqrt{x^2+1}+3-x}=\left(3x-4\right)\left(2x-1\right)\)
<=> \(\frac{\left(4x-1\right)\left(6x-8\right)}{\sqrt{x^2+1}+3-x}-\left(3x-4\right)\left(2x-1\right)=0\)
<=>\(\left(3x-4\right)\left(\frac{2\left(4x-1\right)}{\sqrt{x^2+1}+3-x}-2x+1\right)=0\)
<=>\(\left[{}\begin{matrix}x=\frac{4}{3}\left(tm\right)\\\frac{8x-2}{\sqrt{x^2+1}+3-x}-2x+1=0\left(2\right)\end{matrix}\right.\)
pt (2) <=>\(8x-2=\left(2x-1\right)\sqrt{x^2+1}-2x^2+7x-3\)
<=>\(2x^2+x+1=\left(2x-1\right)\sqrt{x^2+1}\)( đk: \(x\ge\frac{1}{2}\))
=>\(4x^4+x^2+1+4x^3+2x+4x^2=\left(2x-1\right)^2\left(x^2+1\right)\)
<=>\(4x^4+4x^3+5x^2+2x+1=4x^4-4x^3+5x^2-4x+1\)
<=>\(8x^3+6x=0\) <=> \(x\left(8x^2+6\right)=0\) <=>x=0 (do 8x2+6>0) (không t/m (2))
=>(2) vô nghiệm
Vậy pt có tập nghiệm \(S=\left\{\frac{4}{3}\right\}\)
P/s: Hơi dài :)
\(9y^2+\left(2y+3\right)\left(y-x\right)\) nha mn mik ghi sai đề
\(a,ĐK:1\le x\le3\)
Đặt \(\left\{{}\begin{matrix}\sqrt{x-1}=a\\\sqrt{3-x}=b\end{matrix}\right.\left(a,b\ge0\right)\)
\(PT\Leftrightarrow a+b-ab=1\Leftrightarrow a+b-ab-1=0\\ \Leftrightarrow\left(a-1\right)\left(1-b\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}a=1\\b=1\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x-1=1\\3-x=1\end{matrix}\right.\Leftrightarrow x=2\left(tm\right)\)
\(b,ĐK:0\le x\le9\\ PT\Leftrightarrow9+2\sqrt{x\left(9-x\right)}=-x^2+9x+9\\ \Leftrightarrow2\sqrt{-x^2+9x}-\left(-x^2+9x\right)=0\\ \Leftrightarrow\sqrt{-x^2+9x}\left(2-\sqrt{-x^2+9x}\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}-x^2+9x=0\\\sqrt{-x^2+9x}=2\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=9\\x^2-9x+4=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\left(n\right)\\x=9\left(n\right)\\x=\dfrac{9+\sqrt{65}}{2}\left(n\right)\\x=\dfrac{9-\sqrt{65}}{2}\left(n\right)\end{matrix}\right.\)
a/ ĐKXĐ: \(-2\le x\le5\)
\(\sqrt{x+2}+\sqrt{5-x}+\sqrt{\left(x+2\right)\left(5-x\right)}-4=0\)
Đặt \(\sqrt{x+2}+\sqrt{5-x}=a>0\Rightarrow\sqrt{\left(x+2\right)\left(5-x\right)}=\frac{a^2-7}{2}\)
\(\Rightarrow a+\frac{a^2-7}{2}-4=0\)
\(\Leftrightarrow a^2+2a-15=0\Rightarrow\left[{}\begin{matrix}a=3\\a=-5\left(l\right)\end{matrix}\right.\)
\(\Rightarrow\sqrt{\left(x+2\right)\left(5-x\right)}=\frac{a^2-7}{2}=1\)
\(\Leftrightarrow-x^2+3x+10=1\)
\(\Leftrightarrow x^2-3x-9=0\)
b/ \(\Leftrightarrow\sqrt{x+1}-\sqrt{4-x}+2\left(5+2\sqrt{\left(x+1\right)\left(4-x\right)}\right)=17\)
Đặt \(\sqrt{x+1}-\sqrt{4-x}=a\Rightarrow\sqrt{\left(x+1\right)\left(4-x\right)}=\frac{5-a^2}{2}\)
\(a+2\left(5+5-a^2\right)=17\)
\(\Leftrightarrow-2a^2+a+3=0\Rightarrow\left[{}\begin{matrix}a=-1\\a=\frac{3}{2}\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}\sqrt{x+1}-\sqrt{4-x}=-1\\\sqrt{x+1}-\sqrt{4-x}=\frac{3}{2}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}\sqrt{x+1}+1=\sqrt{4-x}\\2\sqrt{x+1}=2\sqrt{4-x}+3\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x+2+2\sqrt{x+1}=4-x\\4x+4=25-4x+12\sqrt{4-x}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}\sqrt{x+1}=1-x\left(x\le1\right)\\12\sqrt{4-x}=8x-21\left(x\ge\frac{21}{8}\right)\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x+1=\left(1-x\right)^2\\144\left(4-x\right)=\left(8x-21\right)^2\end{matrix}\right.\)
c/ ĐKXĐ: \(0\le x\le1\)
Đặt \(\sqrt{x}+\sqrt{1-x}=a>0\Rightarrow\sqrt{x-x^2}=\frac{a^2-1}{2}\)
\(a^2-1=3\left(a-1\right)\Leftrightarrow a^2-3a+2=0\Rightarrow\left[{}\begin{matrix}a=1\\a=2\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}\sqrt{x-x^2}=\frac{a^2-1}{2}=0\\\sqrt{x-x^2}=\frac{a^2-1}{2}=\frac{3}{2}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x-x^2=0\\x-x^2=\frac{9}{4}\left(vn\right)\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x=0\\x=1\end{matrix}\right.\)
d/ ĐKXĐ: ...
Đặt \(\left\{{}\begin{matrix}\sqrt{5+2x}=a\ge0\\\sqrt{5-2x}=b\ge0\end{matrix}\right.\) ta được:
\(\left\{{}\begin{matrix}\left(3a-1\right)\left(3b-1\right)=16\\a^2+b^2=10\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}3ab-\left(a+b\right)=5\\\left(a+b\right)^2-2ab=10\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}a+b=3ab-5\\\left(a+b\right)^2-2ab=10\end{matrix}\right.\)
\(\Rightarrow\left(3ab-5\right)^2-2ab=10\)
\(\Leftrightarrow9\left(ab\right)^2-32ab+15=0\Rightarrow\left[{}\begin{matrix}ab=3\\ab=\frac{5}{9}\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}\left(ab\right)^2=9\\\left(ab\right)^2=\frac{25}{81}\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}25-4x^2=9\\25-4x^2=\frac{25}{81}\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x^2=4\\x^2=\frac{500}{81}\end{matrix}\right.\)
