Nhận thấy : \(x^2+x+1=\left(x-\frac{1}{2}\right)^2+\frac{3}{4}>0\Rightarrow\left|x^2+x+1\right|=x^2+x+1\)

\(x^2+3x+7=\left(x-\frac{3}{2}\right)^2+\frac{19}{4}>0\Rightarrow\left|x^2+3x+7\right|=x^2+3x+7\)

Do đó : \(A=2x^2+4x+8=2\left(x^2+2x+1\right)+6=2\left(x+1\right)^2+6\ge6\)

Dấu đẳng thức xảy ra <=> x = -1

Vậy \(MinA=6\Leftrightarrow x=-1\)

GTNN là 8 nha

\(A=\left(x-1\right)\left(2x-1\right)\left(2x^2-3x-1\right)+2017\)

\(=\left(2x^2-3x+1\right)\left(2x^2-3x-1\right)+2017\)

\(=\left(2x^2-3x\right)^2-1+2017\)

\(=\left(2x^2-3x\right)^2+2016\ge2016\)

\(\Leftrightarrow2x^2-3x=0\Leftrightarrow x\left(2x-3\right)=0\Leftrightarrow\orbr{\begin{cases}x=0\\x=\frac{3}{2}\end{cases}}\)

Vậy \(A_{min}=2016\Leftrightarrow\orbr{\begin{cases}x=0\\x=\frac{3}{2}\end{cases}}\)

ai thấy mình làm đúng thì k cho mình nha!

Lời giải:
$A=(x-1)(x-2)(x-3)(x-4)=[(x-1)(x-4)][(x-2)(x-3)]=(x^2-5x+4)(x^2-5x+6)$

$=a(a+2)$ (đặt $x^2-5x+4=a$)

$=a^2+2a=(a+1)^2-1=(x^2-5x+5)^2-1\geq -1$

Vậy $S_{\min}=-1$. Giá trị này đạt tại $x^2-5x+5=0$

$\Leftrightarrow x=\frac{5\pm \sqrt{5}}{2}$

Giups mik vs

\(=x^2-3x+2=\left(x-\dfrac{3}{2}\right)^2-\dfrac{1}{4}\ge-\dfrac{1}{4}\forall x\)

Dấu '=' xảy ra khi x=3/2

1:

ĐKXĐ: \(x\notin\left\{3;-2;1\right\}\)

 \(A=\left(\dfrac{x\left(x+2\right)-x+1}{\left(x-3\right)\left(x+2\right)}\right):\left(\dfrac{x\left(x-3\right)+5x+1}{\left(x+2\right)\left(x-3\right)}\right)\)

\(=\dfrac{x^2+2x-x+1}{\left(x-3\right)\left(x+2\right)}\cdot\dfrac{\left(x+2\right)\left(x-3\right)}{x^2-3x+5x+1}\)

\(=\dfrac{x^2+x+1}{\left(x-1\right)^2}\)

= \(4x^2\)+\(20x\)+\(25\)+\(6x^2\)- \(8x\)- \(x^2\)-\(22\)

=\(9x^2\)+\(12x\)+\(3\)

=\(9x^2\)+\(12x\)+\(3\)

=\(9x^2\)+\(12x\)+\(4\)-\(1\)

=(\(3x\)+\(2\))²-\(1\)

vì (\(3x\)+\(2\))² >-0

=>.................-\(1\)>-(-1)

(>- là > hoặc =)

=> GTNN của M= -1 khi và chỉ khi \(3x\)+\(2\)=\(0\)

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