(2x-3)^2019=1/4(2x-3)^2017
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Đặt \(2017-x=m,2019-x=n\)
\(\rightarrow m+n=2x-4036\)
Phương trình ban đầu trở thành :
\(m^3+n^3=\left(m+n\right)^3\)
\(\rightarrow3mn.\left(m+n\right)^3=0\)
\(\rightarrow\left(2017-x\right)\left(2019-x\right)\left(2x-4036\right)=0\)
\(\rightarrow\left[{}\begin{matrix}x=2017\\x=2018\\x=2019\end{matrix}\right.\)
Vậy \(S=\left\{2017;2018;2019\right\}\)
(2017-X)3+(2019-X)3+(2X-4036)3=0
<=>(2017-x).(2018-x).(2019-x)=0
<=>x=2017
x=2018
x=2019
#YQ
a) \(22-x\left(1-4x\right)=\left(2x+3\right)^3\)
\(\Leftrightarrow22-x+4x^2=8x^3+36x^2+54x+27\)
\(\Leftrightarrow-x-54x+4x^2-36x^2-8x^3=-22+27\)
\(\Leftrightarrow-8x^3-32x^2-55x=5\Leftrightarrow-8x^3-32x^2-55x-5=0\)
Bn tự làm tiếp nhé
b) \(\frac{2x}{3}+\frac{2x-1}{6}=\frac{4-x}{3}\Leftrightarrow\frac{2.2x}{6}+\frac{2x-1}{6}=\frac{2\left(4-x\right)}{6}\)
\(\Leftrightarrow2.2x+2x-1=2\left(4-x\right)\Leftrightarrow4x+2x-1=8-2x\)
\(\Leftrightarrow6x-1=8-2x\Leftrightarrow8x=9\Leftrightarrow x=\frac{9}{8}\)
Vậy phương trình có tập nghiệm S ={9/8}
c) \(\frac{x-1}{2019}+\frac{x-2}{2018}=\frac{x-3}{2017}+\frac{x-4}{2016}\)
\(\Leftrightarrow\left(\frac{x-1}{2019}-1\right)+\left(\frac{x-2}{2018}-1\right)=\left(\frac{x-3}{2017}-1\right)+\left(\frac{x-4}{2016}-1\right)\)
\(\Leftrightarrow\frac{x-2020}{2019}+\frac{x-2020}{2018}-\frac{x-2020}{2017}-\frac{x-2020}{2016}=0\)
\(\Leftrightarrow\left(x-2020\right)\left(\frac{1}{2019}+\frac{1}{2018}+\frac{1}{2017}+\frac{1}{2016}\right)=0\)
Do \(\frac{1}{2019}+\frac{1}{2018}+\frac{1}{2017}+\frac{1}{2016}>0\)
Nên \(x-2020=0\Leftrightarrow x=2020\)
Đặt 2017-x=a; 2019-x=b
\(\Leftrightarrow a+b=4036-2x\)
\(\Leftrightarrow-\left(a+b\right)=2x-4036\)
Phương trình trở thành: \(a^3+b^3-\left(a+b\right)^3=0\)
\(\Leftrightarrow\left(a+b\right)^3-3ab\left(a+b\right)-\left(a+b\right)^3=0\)
\(\Leftrightarrow-3ab\left(a+b\right)=0\)
mà -3<0
nên \(ab\left(a+b\right)=0\)
\(\Leftrightarrow\left(2017-x\right)\left(2019-x\right)\left(4036-2x\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}2017-x=0\\2019-x=0\\4036-2x=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2017\\x=2019\\x=2018\end{matrix}\right.\)
Vậy: S={2017;2018;2019}
Cho \(\left(2017-x\right)^3=x;\left(2019-x\right)^3=y;\left(2x-4036\right)^3=z\)
Ta có: \(x+y+z=0\)
\(=>x+y=-z\) \(=>\left(x+y\right)^3=-z^3\)
Ta có: \(x^3+y^3+z^3=\left(x+y\right)^3-3xy\left(x+y\right)+z^3=-z^3-3xy\left(-z\right)+z^3=3xyz\)
Vì (2017-x)3 + (2019-x)3 + (2x-4036)3 =0
=>\(3\left(2017-x\right)\left(2019-x\right)\left(2x-4036\right)=0\)
Gải phương trình được x=2017; x=2019; x=2018
a: =>x-2017=0 và y-2018=0
=>x=2017; y=2018
b: =>3x-y=0 và y+2/3=0
=>y=-2/3 và 3x=-2/3
=>x=-2/9 và y=-2/3
c: =>3/4x-1/2=0 và 4/5y+6/25=0
=>x=2/3 và y=-3/10
b. \(\left(2x+1\right)+\left(4x+3\right)+\left(6x+5\right)+...+\left(100x+99\right)=7600\)
\(\rightarrow\left(2x+4x+6x+...+100x\right)+\left(1+3+5+...+99\right)=7600\)
\(\rightarrow\frac{\left(2x+100x\right).50}{2}+\frac{\left(1+99\right).50}{2}=7600\)
\(\rightarrow51x.50+50.50=7600\)
\(\rightarrow51x.50+2500=7600\)
\(\rightarrow51x.50=7600-2500\)
\(\rightarrow51x.50=5100\)
\(\rightarrow50x=100\)
\(\rightarrow x=\frac{100}{50}=2\)
Vậy x = 2
\(\Leftrightarrow\left(2x-3\right)\left(2x-\dfrac{7}{2}\right)\left(2x-\dfrac{5}{2}\right)=0\)
\(\Leftrightarrow x\in\left\{\dfrac{3}{2};\dfrac{7}{4};\dfrac{5}{4}\right\}\)