4x . 4 =16
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Lời giải:
$x^2=4.4.4.4=16.16=(-16)(-16)=16^2=(-16)^2$
$\Rightarrow x=16$ hoặc $x=-16$.
Lời giải:
a. ĐKXĐ: $x\in\mathbb{R}$
PT $\Leftrightarrow \sqrt{(x-2)^2}=5$
$\Leftrightarrow |x-2|=5$
$\Leftrightarrow x-2=5$ hoặc $x-2=-5$
$\Leftrightarrow x=7$ hoặc $x=-3$ (đều tm)
b. ĐKXĐ: $x\geq -1$
PT $\Leftrightarrow \sqrt{16}.\sqrt{x+1}-3\sqrt{x+1}+\sqrt{4}.\sqrt{x+1}=16-\sqrt{x+1}$
$\Leftrightarrow 4\sqrt{x+1}-3\sqrt{x+1}+2\sqrt{x+1}=16-\sqrt{x+1}$
$\Leftrightarrow 4\sqrt{x+1}=16$
$\Leftrightarrow \sqrt{x+1}=4$
$\Leftrightarrow x+1=16$
$\Leftrightarrow x=15$ (tm)
\(A=\left(\dfrac{1}{x^2-4x}+\dfrac{2}{16-x^2}+\dfrac{4}{4x+16}\right):\dfrac{1}{4x}\left(x\ne4;x\ne-4;x\ne0\right).\)
\(A=\left(\dfrac{1}{x\left(x-4\right)}+\dfrac{-2}{\left(x+4\right)\left(x-4\right)}+\dfrac{1}{x+4}\right).4x\).
\(A=\dfrac{x+4-2x+x^2-4x}{x\left(x-4\right)\left(x+4\right)}.4x.\)
\(A=\dfrac{x^2-5x+4}{\left(x-4\right)\left(x+4\right)}.4.\)
\(A=\dfrac{\left(x-4\right)\left(x-1\right)}{\left(x-4\right)\left(x+4\right)}.4.\)
\(A=\dfrac{4\left(x-1\right)}{x+4}.\)
(x+4)(x2 -4x-4x+16)
=(x+4)(x2 -8x+16)
=(x-8x)(4+16)(x2)
=-7x.20.x2
=>sap xep x2.(-7x).20
chuc ban hoc tot
a) \(\sqrt{x-1}+\sqrt{4x-4}-\sqrt{25x-25}+2=0\) (ĐK: \(x\ge1\))
\(\Leftrightarrow\sqrt{x-1}+\sqrt{4\left(x-1\right)}-\sqrt{25\left(x-1\right)}+2=0\)
\(\Leftrightarrow\sqrt{x-1}+2\sqrt{x-1}-5\sqrt{x-1}+2=0\)
\(\Leftrightarrow-2\sqrt{x-1}=-2\)
\(\Leftrightarrow\sqrt{x-1}=\dfrac{2}{2}\)
\(\Leftrightarrow\sqrt{x-1}=1\)
\(\Leftrightarrow x-1=1\)
\(\Leftrightarrow x=2\left(tm\right)\)
b) \(\sqrt{16x+16}-\sqrt{9x+9}+\sqrt{4x+4}+\sqrt{x+1}=16\) (ĐK: \(x\ge-1\))
\(\Leftrightarrow\sqrt{16\left(x+1\right)}-\sqrt{9\left(x+1\right)}+\sqrt{4\left(x+1\right)}+\sqrt{x+1}=16\)
\(\Leftrightarrow4\sqrt{x+1}-3\sqrt{x+1}+2\sqrt{x+1}+\sqrt{x+1}=16\)
\(\Leftrightarrow4\sqrt{x+1}=16\)
\(\Leftrightarrow\sqrt{x+1}=4\)
\(\Leftrightarrow x+1=16\)
\(\Leftrightarrow x=15\left(tm\right)\)
\(4x^4-16-4x^2-16x\)
\(=4x^2\left(x^2-1\right)-16\left(1+x\right)\)
\(=4x^2\left(x+1\right)\left(x-1\right)-16\left(x+1\right)\)
\(=\left(x+1\right)\left[4x^2\left(x-1\right)-16\right]\)
\(=\left(x+1\right)4\left[x^2\left(x-1\right)-4\right]\)
Nguyễn Văn Tuấn AnhNs r, không biết thì not làm
\(4x^4-16-4x^2-16x\)
\(=4x^2\left(x^2-1\right)-16\left(x+1\right)\)
\(=4x^2\left(x-1\right)\left(x+1\right)-16\left(x+1\right)\)
\(=\left(x+1\right)\left[4x^2\left(x-1\right)-16\right]\)
\(=4\left(x+1\right)\left[x^2\left(x-1\right)-4\right]\)
\(=4\left(x+1\right)\left[x^3-x^2-4\right]\)
\(=4\left(x+1\right)\left[x^3+x^2+2x-2x^2-2x-4\right]\)
\(=4\left(x+1\right)\left[x\left(x^2+x+2\right)-2\left(x^2+x+2\right)\right]\)
\(=4\left(x+1\right)\left(x-2\right)\left(x^2+x+2\right)\)
4\(^x\) : 4 = 16
4\(^x\) = 16.4
4\(^x\) = 64
4\(^x\) = 4\(^3\)
=> x=3