|x+2| + |x+3| = 3/4x
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HT
0
28 tháng 2 2020
d) đề là gì bn
(4x−1)3−(4x−3)(16x2+3)
=64x3−48x2+12x−1−(64x3+12x−48x2−9)
=64x3−48x2+12x−1−64x3−12x+48x2+9
=8
29 tháng 2 2020
\(c, C=x(2x+1)-x^2(x+2)+x^3-x+3\)
\(C=2x^2+x-x^3-2x^2+x^3-x+3\)
\(C=3\)
\(d, (2x+3)(4x^2-6x+9)-2(4x^3-1)\)
\(=(8x^3+27)-2(4x^3-1)\)
\(=8x^3+27-8x^3+2\)\(=29\)
\(e, (4x-1)^3-(4x-3)(16x^2+3)\)
\(=(64x^3-48x^2+12x-1)-(64x^3+12x-48x^2-9)\)
\(=64x^3-48x^2+12x-1-64x^3-12x+48x^2+9\)
\(=8\)
\(f, (x+1)^3-(x-1)^3-6(x+1)(x-1)\)
\(=(x^3+3x^2+3x+1)-(x^3-3x^2+3x-1)-6(x^2-1)\)
\(=x^3+3x^2+3x+1-x^3+3x^2-3x+1-6x^2+6\)
\(=8\)
HT
2
HP
2 tháng 2 2021
1.
\(x^4-6x^2-12x-8=0\)
\(\Leftrightarrow x^4-2x^2+1-4x^2-12x-9=0\)
\(\Leftrightarrow\left(x^2-1\right)^2=\left(2x+3\right)^2\)
\(\Leftrightarrow\left[{}\begin{matrix}x^2-1=2x+3\\x^2-1=-2x-3\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x^2-2x-4=0\\x^2+2x+2=0\end{matrix}\right.\)
\(\Leftrightarrow x=1\pm\sqrt{5}\)
HP
2 tháng 2 2021
3.
ĐK: \(x\ge-9\)
\(x^4-x^3-8x^2+9x-9+\left(x^2-x+1\right)\sqrt{x+9}=0\)
\(\Leftrightarrow\left(x^2-x+1\right)\left(\sqrt{x+9}+x^2-9\right)=0\)
\(\Leftrightarrow\sqrt{x+9}+x^2-9=0\left(1\right)\)
Đặt \(\sqrt{x+9}=t\left(t\ge0\right)\Rightarrow9=t^2-x\)
\(\left(1\right)\Leftrightarrow t+x^2+x-t^2=0\)
\(\Leftrightarrow\left(x+t\right)\left(x-t+1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-t\\x=t-1\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-\sqrt{x+9}\\x=\sqrt{x+9}-1\end{matrix}\right.\)
\(\Leftrightarrow...\)
TA
1
10 tháng 8 2017
\(\left(x-3\right)^3+\left(x+3\right)^3=0\)
\(\Leftrightarrow x^3-9x^2+27x-27+x^3+9x^2+27x+27=0\)\(\Leftrightarrow2x^3+54x^2=0\)
\(\Leftrightarrow x^2\left(2x+54\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=0\\2x+54=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=0\\x=-27\end{matrix}\right.\)
\(b,\left(x+1\right)^3-\left(x-1\right)^3=0\)
\(\Leftrightarrow x^3+3x^2+3x+1-x^3+3x^2-3x+1=0\)\(\Leftrightarrow6x^2+2=0\)
\(\Leftrightarrow6x^2=-2\)
\(\Leftrightarrow x^2=-3\) ( vô lí)
Vậy pt vô nghiệm
\(c,x^2-4x+3=0\)
\(\Leftrightarrow x^2-3x-x+3=0\)
\(\Leftrightarrow x\left(x-3\right)-\left(x-3\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left(x-3\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-1=0\\x-3=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=1\\x=3\end{matrix}\right.\)
\(d,4x^2+4x+1=0\)
\(\Leftrightarrow\left(2x+1\right)^2=0\)
\(\Rightarrow2x+1=0\)
\(\Leftrightarrow2x=-1\Rightarrow x=-\dfrac{1}{2}\)
\(e,\left(x+2\right)^2-\left(x+3\right)^2=0\)
\(\Leftrightarrow\left(x+2-x-3\right)\left(x+2+x+3\right)=0\)
\(\Leftrightarrow-\left(2x+5\right)=0\)
\(\Leftrightarrow-2x-5=0\)
\(\Leftrightarrow-2x=5\Rightarrow x=-\dfrac{5}{2}\)
Học tốt nha you <3
TA
1
10 tháng 8 2017
\(\left(x-3\right)^3+\left(x+3\right)^3=0\)
\(\Leftrightarrow x^3-9x^2+27x-27+x^3+9x^2+27x+27=0\)\(\Leftrightarrow2x^3+54x^2=0\)
\(\Leftrightarrow x^2\left(2x+54\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=0\\2x+54=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=0\\x=-27\end{matrix}\right.\)
\(b,\left(x+1\right)^3-\left(x-1\right)^3=0\)
\(\Leftrightarrow x^3+3x^2+3x+1-x^3+3x^2-3x+1=0\)\(\Leftrightarrow6x^2+2=0\)
\(\Leftrightarrow6x^2=-2\)
\(\Leftrightarrow x^2=-3\) ( vô lí)
Vậy pt vô nghiệm
\(c,x^2-4x+3=0\)
\(\Leftrightarrow x^2-3x-x+3=0\)
\(\Leftrightarrow x\left(x-3\right)-\left(x-3\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left(x-3\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-1=0\\x-3=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=1\\x=3\end{matrix}\right.\)
\(d,4x^2+4x+1=0\)
\(\Leftrightarrow\left(2x+1\right)^2=0\)
\(\Rightarrow2x+1=0\)
\(\Leftrightarrow2x=-1\Rightarrow x=-\dfrac{1}{2}\)
\(e,\left(x+2\right)^2-\left(x+3\right)^2=0\)
\(\Leftrightarrow\left(x+2-x-3\right)\left(x+2+x+3\right)=0\)
\(\Leftrightarrow-\left(2x+5\right)=0\)
\(\Leftrightarrow-2x-5=0\)
\(\Leftrightarrow-2x=5\Rightarrow x=-\dfrac{5}{2}\)
Học tốt nha you <3
TA
1
10 tháng 8 2017
\(\left(x-3\right)^3+\left(x+3\right)^3=0\)
\(\Leftrightarrow x^3-9x^2+27x-27+x^3+9x^2+27x+27=0\)\(\Leftrightarrow2x^3+54x^2=0\)
\(\Leftrightarrow x^2\left(2x+54\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=0\\2x+54=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=0\\x=-27\end{matrix}\right.\)
\(b,\left(x+1\right)^3-\left(x-1\right)^3=0\)
\(\Leftrightarrow x^3+3x^2+3x+1-x^3+3x^2-3x+1=0\)\(\Leftrightarrow6x^2+2=0\)
\(\Leftrightarrow6x^2=-2\)
\(\Leftrightarrow x^2=-3\) ( vô lí)
Vậy pt vô nghiệm
\(c,x^2-4x+3=0\)
\(\Leftrightarrow x^2-3x-x+3=0\)
\(\Leftrightarrow x\left(x-3\right)-\left(x-3\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left(x-3\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-1=0\\x-3=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=1\\x=3\end{matrix}\right.\)
\(d,4x^2+4x+1=0\)
\(\Leftrightarrow\left(2x+1\right)^2=0\)
\(\Rightarrow2x+1=0\)
\(\Leftrightarrow2x=-1\Rightarrow x=-\dfrac{1}{2}\)
\(e,\left(x+2\right)^2-\left(x+3\right)^2=0\)
\(\Leftrightarrow\left(x+2-x-3\right)\left(x+2+x+3\right)=0\)
\(\Leftrightarrow-\left(2x+5\right)=0\)
\(\Leftrightarrow-2x-5=0\)
\(\Leftrightarrow-2x=5\Rightarrow x=-\dfrac{5}{2}\)
Học tốt nha you <3
