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2x^2+9=0=>2x^2=-9 =>x^2=-9\2 Vì x^2>0 nên kh tìm đc x
16 tháng 5 2021

ok cảm ơn

công nhận nó dễ thật

21 tháng 5 2017

\(M=4x^2-10x+\frac{9}{2x}+2018\)

\(=4x^2-12x+2x+\frac{9}{2x}+2018\)

\(=\left(4x^2-12x+9\right)+\left(2x+\frac{9}{2x}\right)+2009\)

\(=\left[\left(2x\right)^2-2.2x.3+3^2\right]+\left(2x+\frac{9}{2x}\right)+2009\)

\(=\left(2x-3\right)^2+\left(2x+\frac{9}{2x}\right)+2009\)

Ta có : \(2x+\frac{9}{2x}\ge2\sqrt{2x\cdot\frac{9}{2x}}=2.\sqrt{9}=6\)

\(\Rightarrow M\ge\left(2x-3\right)^2+6+2009\ge2015\)

Dấu "=" xảy ra <=> \(x=\frac{3}{2}\)

Vậy GTNN của M là \(2015\) tại \(x=\frac{3}{2}\)

21 tháng 5 2017

Min M=2009

14 tháng 10 2018

Bo may la binh day k di hieu ashdbfgbgygygggydfsghuyfhdguuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu3

Ta có: \(\Delta=-7k^2-42k+49\)

Để phương trình có nghiệm kép \(\Leftrightarrow\Delta=-7k^2-42k+49=0\) \(\Leftrightarrow\left[{}\begin{matrix}k=1\\k=-7\end{matrix}\right.\)

  Vậy ...

20 tháng 5 2021

Cái phương trình đầu tiên ở đâu ra vậy ? 

18 tháng 9 2021

Ta có: 

\(y=3x\left(k^2-k+1\right)=-2\)

\(\Rightarrow3\left(-3\right)\left(k^2-k+1\right)=-2\)

\(\Rightarrow-9\left(k^2-k+1\right)=-2\)

\(\Rightarrow k^2-k+1=\frac{2}{9}\)

\(\Rightarrow\left(k-\frac{1}{2}\right)^2=\frac{2}{9}-\frac{3}{4}=\frac{35}{36}\) (Vô nghiệm)