53+12+23-12-32+2=????

Ta có 2*(5*x) = 1

<=> 3.2 - (5*x) = 1

<=> 6 - (3.5 - x) = 1

<=> 6 - (15-x) = 1

<=> 6 - 15 + x = 1

<=>  (-9) + x = 1

<=> x = 10

3700 hoặc 3699

đoạn sau là x²-ax-1/(2a²)=0 nha, viết thiếu.

@nguyenthanhtuan cái này là chứng minh mà bạn.

Đáp án A 

\(\left(x+y+z\right).\left(\dfrac{1}{x+y}+\dfrac{1}{y+z}+\dfrac{1}{x+z}\right)=\dfrac{2017}{672}\)

\(\Rightarrow\left(\dfrac{x+y+z}{x+y}+\dfrac{x+y+z}{y+z}+\dfrac{x+y+z}{x+z}\right)=\dfrac{2017}{672}\)

\(\Rightarrow1+\dfrac{z}{x+y}+1+\dfrac{x}{y+z}+1+\dfrac{y}{x+z}=\dfrac{2017}{672}\)

\(\Rightarrow3+\dfrac{x}{y+z}+\dfrac{y}{x+z}+\dfrac{z}{x+y}=\dfrac{2017}{672}\)

\(\Rightarrow\dfrac{x}{y+z}+\dfrac{y}{x+z}+\dfrac{z}{x+y}=\dfrac{2017}{672}-3=\dfrac{2017}{672}-\dfrac{2016}{672}=\dfrac{1}{672}\)

\(\Rightarrow C=\dfrac{1}{672}\)

a: y=2 thì \(A=\dfrac{x+2}{2-1}=x+2\)

\(B=\dfrac{4x\left(x+5\right)}{2+2}=x\left(x+5\right)\)

A+3=B

=>x+5=x(x+5)

=>(x+5)(1-x)=0

=>x=1 hoặc x=-5

b: Khi x=-3 thì \(A=\dfrac{-3+2}{y-1}=\dfrac{-1}{y-1}\)

\(B=\dfrac{4\cdot\left(-3\right)\cdot\left(-3+5\right)}{y+2}=\dfrac{-12\cdot2}{y+2}=\dfrac{-24}{y+2}\)

A-B=13

\(\Leftrightarrow-\dfrac{1}{y-1}+\dfrac{24}{y+2}=13\)

\(\Leftrightarrow13\left(y-1\right)\left(y+2\right)=-y-2+24y-24\)

\(\Leftrightarrow13y^2+13y-26=23y-26\)

=>y(13y-10)=0

=>y=0 hoặc y=10/13