`a)TXĐ:R\\{1;1/3}`

`y'=[-4(6x-4)]/[(3x^2-4x+1)^5]`

`b)TXĐ:R`

`y'=2x. 3^[x^2-1] ln 3-e^[-x+1]`

`c)TXĐ: (4;+oo)`

`y'=[2x-4]/[x^2-4x]+2/[(2x-1).ln 3]`

`d)TXĐ:(0;+oo)`

`y'=ln x+2/[(x+1)^2].2^[[x-1]/[x+1]].ln 2`

`e)TXĐ:(-oo;-1)uu(1;+oo)`

`y'=-7x^[-8]-[2x]/[x^2-1]`

Lời giải:
a.

$y'=-4(3x^2-4x+1)^{-5}(3x^2-4x+1)'$

$=-4(3x^2-4x+1)^{-5}(6x-4)$

$=-8(3x-2)(3x^2-4x+1)^{-5}$

b.

$y'=(3^{x^2-1})'+(e^{-x+1})'$

$=(x^2-1)'3^{x^2-1}\ln 3 + (-x+1)'e^{-x+1}$

$=2x.3^{x^2-1}.\ln 3 -e^{-x+1}$

c.

$y'=\frac{(x^2-4x)'}{x^2-4x}+\frac{(2x-1)'}{(2x-1)\ln 3}$

$=\frac{2x-4}{x^2-4x}+\frac{2}{(2x-1)\ln 3}$

d.

\(y'=(x\ln x)'+(2^{\frac{x-1}{x+1}})'=x(\ln x)'+x'\ln x+(\frac{x-1}{x+1})'.2^{\frac{x-1}{x+1}}\ln 2\)

\(=x.\frac{1}{x}+\ln x+\frac{2}{(x+1)^2}.2^{\frac{x-1}{x+1}}\ln 2\\ =1+\ln x+\frac{2^{\frac{2x}{x+1}}\ln 2}{(x+1)^2}\)

e.

\(y'=-7x^{-8}-\frac{(x^2-1)'}{x^2-1}=-7x^{-8}-\frac{2x}{x^2-1}\)

\(a,y'=8x^3-9x^2+10x\\ \Rightarrow y''=24x^2-18x+10\\ b,y'=\dfrac{2}{\left(3-x\right)^2}\\ \Rightarrow y''=\dfrac{4}{\left(3-x\right)^3}\)

\(c,y'=2cos2xcosx-sin2xsinx\\ \Rightarrow y''=-5sin\left(2x\right)cos\left(x\right)-4cos\left(2x\right)sin\left(x\right)\\ d,y'=-2e^{-2x+3}\\ \Rightarrow y''=4e^{-2x+3}\)

e,

\(y = \ln (x + 1) \Rightarrow y' = \frac{1}{{x + 1}} \Rightarrow y'' =  - \frac{1}{{{{\left( {x + 1} \right)}^2}}}\)

f,

\(y = \ln ({e^x} + 1) \Rightarrow y' = \frac{{{e^x}}}{{{e^x} + 1}} \Rightarrow y'' =  - \frac{{{e^x}.{e^x}}}{{{{\left( {{e^x} + 1} \right)}^2}}} =  - \frac{{{e^{2x}}}}{{{{\left( {{e^x} + 1} \right)}^2}}}\)

Đáp án B

Ta có ln   x y = ln   x + ln   y ≥ ln x 2 + y

⇔ x y ≥ x 2 + y ⇔ y x - 1 ≥ x 2

Vì x = 1 không thỏa và y > 0 => x > 1

⇒ P = x y ≥ x 2 x - 1 + x = f x

X é t   h à m   s ố   f x = x 2 x - 1 + x   v ớ i   x > 1

⇒ f ' x = x 2 - 2 x x - 1 2 + x = 2 x 2 - 4 x + 1 x - 1 2

⇒ f ' x = 0 ⇔ x = 2 + 2 2   v ì   x > 1

Dựa vào bảng biến thiên của hàm số f(x) suy ra

⇒ M i n P = M i n x > 1 f x = f 1 = 3 + 2 2 .

g: \(y=ln\left(x^2+x+1\right)\)

=>\(y'=\dfrac{\left(x^2+x+1\right)'}{x^2+x+1}=\dfrac{2x+1}{x^2+x+1}\)

l: \(y=\dfrac{lnx}{x+1}\)

=>\(y'=\dfrac{\left(lnx\right)'\cdot\left(x+1\right)-\left(x+1\right)'\left(lnx\right)}{\left(x+1\right)^2}\)

=>\(y'=\dfrac{\dfrac{1}{x}\left(x+1\right)-lnx}{\left(x+1\right)^2}\)

\(\Leftrightarrow y'=\dfrac{\dfrac{\left(x+1\right)}{x}-lnx}{\left(x+1\right)^2}\)

1.

\(y'=\left(\dfrac{x}{lnx}\right)'.3^{\dfrac{x}{lnx}}.ln3=\dfrac{lnx-1}{ln^2x}.3^{\dfrac{x}{lnx}}.ln3\)

2.

\(y'=\left(tanx\right)'.tanx+\left(tanx\right)'.\dfrac{1}{tanx}=\dfrac{tanx}{cos^2x}+\dfrac{1}{tanx.cos^2x}\)

3.

\(y=\left(ln2x\right)^{\dfrac{2}{3}}\Rightarrow y'=\left(ln2x\right)'.\dfrac{2}{3}.\left(ln2x\right)^{-\dfrac{1}{3}}=\dfrac{1}{3x\sqrt[3]{ln2x}}\)

a: \(y'=4\cdot3x^2-3\cdot2x+2=12x^2-6x+2\)

b: \(y'=\dfrac{\left(x+1\right)'\left(x-1\right)-\left(x+1\right)\left(x-1\right)'}{\left(x-1\right)^2}=\dfrac{x-1-x-1}{\left(x-1\right)^2}=\dfrac{-2}{\left(x-1\right)^2}\)

c: \(y'=-2\cdot\left(\sqrt{x}\cdot x\right)'\)

\(=-2\cdot\left(\dfrac{x+x}{2\sqrt{x}}\right)=-2\cdot\dfrac{2x}{2\sqrt{x}}=-2\sqrt{x}\)

d: \(y'=\left(3sinx+4cosx-tanx\right)\)'

\(=3cosx-4sinx+\dfrac{1}{cos^2x}\)

e: \(y'=\left(4^x+2e^x\right)'\)

\(=4^x\cdot ln4+2\cdot e^x\)

f: \(y'=\left(x\cdot lnx\right)'=lnx+1\)

\(a,4^x-2^{x+1}\ge0\\ \Leftrightarrow2^{x+1}\le2^{2x}\\ \Leftrightarrow x+1\le2x\\ \Leftrightarrow x\ge1\)

Tập xác định của hàm số là D = \([1;+\infty)\)

\(b,\left\{{}\begin{matrix}x>0\\1-ln\left(x\right)>0\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}x>0\\ln\left(x\right)< 1\end{matrix}\right.\\ \Leftrightarrow0< x< e\)

Tập xác định của hàm số là \(\left(0;e\right)\)

a: \(y=x\cdot e^{2x}\)

=>\(y'=\left(x\cdot e^{2x}\right)'\)

\(=x\cdot\left(e^{2x}\right)'+x'\cdot\left(e^{2x}\right)\)

\(=e^{2x}+2\cdot x\cdot e^{2x}\)

\(y''=\left(e^{2x}+2\cdot x\cdot e^{2x}\right)'\)

\(=\left(e^{2x}\right)'+\left(2\cdot x\cdot e^{2x}\right)'\)

\(=4\cdot e^{2x}+4\cdot x\cdot e^{2x}\)

b: \(y=ln\left(2x+3\right)\)

=>\(y'=\dfrac{\left(2x+3\right)'}{\left(2x+3\right)}=\dfrac{2}{2x+3}\)

=>\(y''=\left(\dfrac{2}{2x+3}\right)'=\dfrac{2\left(2x+3\right)'-2'\left(2x+3\right)}{\left(2x+3\right)^2}\)

\(=\dfrac{4}{\left(2x+3\right)^2}\)

a.

\(y'=\dfrac{\left(1+\sqrt{3x-1}\right)'}{1+\sqrt{3x-1}}=\dfrac{3}{2\left(1+\sqrt{3x-1}\right)\sqrt{3x-1}}\)

b.

\(y'=\dfrac{\left(2sin^2x-1\right)'}{\left(2sin^2x-1\right).ln10}=\dfrac{2sin2x}{\left(2sin^2x-1\right)ln10}\)

c.

\(y'=\left(3x^2+3\right)3^{x^3+3x+1}.e^x.ln3+3^{x^3+3x+1}.e^x\)