Đề như này đúng chưa ạ?: (x-2)(x² + 2x+4) - 128 + x³

=x³ - 2³ - 128 + x³

= 2x³ -136 

mình ko biết bn ơi :)

cậu có thể viết lại cho dễ hiểu hơn ko?

\(\frac{\sqrt{x}}{\sqrt{x}-1}\)\(-\frac{1}{x-\sqrt{x}}\)

Giúp tớ với

a: ĐKXĐ: x∉{1;-1;2}

\(P=\left(\frac{x}{x+1}-\frac{1}{1-x}+\frac{1}{1-x^2}\right):\frac{x-2}{x^2-1}\)

\(=\left(\frac{x}{x+1}+\frac{1}{x-1}-\frac{1}{\left(x-1\right)\left(x+1\right)}\right)\cdot\frac{\left(x-1\right)\left(x+1\right)}{x-2}\)

\(=\frac{x\left(x-1\right)+x+1-1}{\left(x-1\right)\left(x+1\right)}\cdot\frac{\left(x-1\right)\left(x+1\right)}{x-2}\)

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

b: Để P nguyên thì \(x^2\) ⋮x-2

=>\(x^2-4+4\) ⋮x-2

=>4⋮x-2

=>x-2∈{1;-1;2;-2;4;-4}

=>x∈{3;1;4;0;6;-2}

Kết hợp ĐKXĐ, ta được: x∈{3;4;0;6;-2}

c: \(P=\frac{x^2}{x-2}\)

\(=\frac{x^2-4+4}{x-2}=x+2+\frac{4}{x-2}=x-2+\frac{4}{x-2}+4\ge2\cdot\sqrt{\left(x-2\right)\cdot\frac{4}{x-2}}+4\)

=>P>=2*2+4=8

Dấu '=' xảy ra khi \(\left(x-2\right)^2=4\)

=>x-2=2

=>x=4(nhận)

giúp mk vs nha , mk đăng cần rất gấp

mình hk bít vít

Bài làm:

Ta có: \(\frac{x-1}{3}+\frac{x-3}{4}=2\)

\(\Leftrightarrow\left(\frac{x}{3}+\frac{x}{4}\right)=2+\frac{1}{3}+\frac{3}{4}\)

\(\Leftrightarrow\frac{7}{12}x=\frac{37}{12}\)

\(\Leftrightarrow x=\frac{37}{12}\div\frac{7}{12}\)

\(\Rightarrow x=\frac{37}{7}\)

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

\(\Leftrightarrow\frac{4\left(x-1\right)}{12}+\frac{3\left(x-3\right)}{12}=\frac{24}{12}\)

\(\Leftrightarrow4\left(x-1\right)+3\left(x-3\right)=24\)

\(\Leftrightarrow4x-4+3x-9=24\)

\(\Leftrightarrow7x-13=24\)

\(\Leftrightarrow7x=37\)

\(\Leftrightarrow x=\frac{37}{7}\)

Đề sai rồi bạn

`B=(1/(3-sqrtx)-1/(3+sqrtx))*(3+sqrtx)/sqrtx(x>=0,x ne 9)`

`B=((3+sqrtx)/(9-x)-(3-sqrtx)/(9-x))*(3+sqrtx)/sqrtx`

`B=((3+sqrtx-3+sqrtx)/(9-x))*(3+sqrtx)/sqrtx`

`B=(2sqrtx)/((3-sqrtx)(3+sqrtx))*(3+sqrtx)/sqrtx`

`B=2/(3-sqrtx)`

`B>1/2`

`<=>2/(3-sqrtx)-1/2>0`

`<=>(4-3+sqrtx)/[2(3-sqrtx)]>0`

`<=>(sqrtx+1)/(2(3-sqrtx))>0`

Mà `sqrtx+1>=1>0`

`<=>2(3-sqrtx)>0`

`<=>3-sqrtx>0`

`<=>sqrtx<3`

`<=>x<9`