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a: \(x^4=5x^2+2x-3\)
=>\(x^4-5x^2-2x+3=0\)
=>\(x^4+x^3-x^2-x^3-x^2+x-3x^2-3x+3=0\)
=>\(\left(x^2+x-1\right)\left(x^2-x-3\right)=0\)
TH1: \(x^2+x-1=0\)
=>\(x^2+x+\frac14=\frac54\)
=>\(\left(x+\frac12\right)^2=\frac54\)
=>\(x+\frac12=\pm\frac{\sqrt5}{2}\)
=>\(x=-\frac12\pm\frac{\sqrt5}{2}\)
TH2: \(x^2-x-3=0\)
=>\(x^2-x+\frac14-\frac{13}{4}=0\)
=>\(\left(x-\frac12\right)^2=\frac{13}{4}\)
=>\(x-\frac12=\pm\frac{\sqrt{13}}{2}\)
=>\(x=\frac12\pm\frac{\sqrt{13}}{2}\)
c: \(3x^3+3x^2+3x=-1\)
=>\(x^3+3x^2+3x+1=-2x^3\)
=>\(\left(x+1\right)^3=\left(x\cdot\sqrt[3]{-2}\right)^3\)
=>\(x+1=x\cdot\sqrt[3]{-2}\)
=>\(x\left(1-\sqrt[3]{-2}\right)=-1\)
=>\(x=\frac{-1}{1-\sqrt[3]{-2}}\)
d: \(8x^3-12x^2+6x-5=0\)
=>\(8x^3-12x^2+6x-1-4=0\)
=>\(\left(2x-1\right)^3=4\)
=>\(2x-1=\sqrt[3]{4}\)
=>\(2x=1+\sqrt[3]{4}\)
=>\(x=\frac12+\frac12\cdot\sqrt[3]{4}\)
1. \(x^3-6x^2+10x-4=0\)
<=> \(\left(x^3-2x^2\right)-\left(4x^2-8x\right)+\left(2x-4\right)=0\)
<=> \(\left(x-2\right)\left(x^2-4x+2\right)=0\)
<=> \(\orbr{\begin{cases}x=2\\x^2-4x+2=0\left(1\right)\end{cases}}\)
Giải pt (1): \(\Delta=\left(-4\right)^2-4.2=8>0\)
=> pt (1) có 2 nghiệm: \(x_1=\frac{4+\sqrt{8}}{2}=2+\sqrt{2}\)
\(x_2=\frac{4-\sqrt{8}}{2}=2-\sqrt{2}\)
1) Ta có: \(x^3-6x^2+10x-4=0\)
\(\Leftrightarrow\left(x^3-2x^2\right)-\left(4x^2-8x\right)+\left(2x-4\right)=0\)
\(\Leftrightarrow x^2\left(x-2\right)-4x\left(x-2\right)+2\left(x-2\right)=0\)
\(\Leftrightarrow\left(x^2-4x+2\right)\left(x-2\right)=0\)
+ \(x-2=0\)\(\Leftrightarrow\)\(x=2\)\(\left(TM\right)\)
+ \(x^2-4x+2=0\)\(\Leftrightarrow\)\(\left(x^2-4x+4\right)-2=0\)
\(\Leftrightarrow\)\(\left(x-2\right)^2=2\)
\(\Leftrightarrow\)\(x-2=\pm\sqrt{2}\)
\(\Leftrightarrow\)\(\orbr{\begin{cases}x=2+\sqrt{2}\approx3,4142\left(TM\right)\\x=2-\sqrt{2}\approx0,5858\left(TM\right)\end{cases}}\)
Vậy \(S=\left\{0,5858;2;3,4142\right\}\)
1)\(\sqrt{4x^2+12x+9}=2-x\)
\(\Leftrightarrow\sqrt{\left(2x+3\right)^2}=2-x\)
\(\Leftrightarrow\left|2x+3\right|=2-x\)
\(\Leftrightarrow\left[{}\begin{matrix}2x+3=2-x\\2x+3=x-2\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}3x=-1\\x=-5\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{1}{3}\\x=-5\end{matrix}\right.\)
\(\)
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