\(x^2-1=\sqrt{x+1}\)

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

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

\(x\left(x^3-2x-1\right)=0\)

\(x^3-x-x-1=0\)

\(x\left(x-1\right)\left(x+1\right)-\left(x+1\right)=0\)

\(\left(x+1\right)\left(x^2-x-1\right)=0\)

\(\left(x+1\right)\left(x^2-x+\dfrac{1}{4}-\dfrac{5}{4}\right)=0\)

=> x+1=0       hoặc        \(\left(x-\dfrac{1}{2}\right)^2-\dfrac{5}{4}=0\)

      x=-1                           \(\left(x-\dfrac{1}{2}\right)^2=\dfrac{5}{4}\)

                                    => \(x=\dfrac{\sqrt{5}+1}{2}\)    hoặc    \(x=-\dfrac{\sqrt{5}-1}{2}\)

Vậy...

\(B=\dfrac{a\sqrt{b}-b\sqrt{a}}{\sqrt{ab}}:\dfrac{1}{\sqrt{a}.\sqrt{b}}\)

\(B=\dfrac{a\sqrt{b}-b\sqrt{a}}{\sqrt{ab}}.\sqrt{ab}\)

\(B=a\sqrt{b}-b\sqrt{a}\)

\(\left(10x+9\right)x-\left(5x-1\right)\left(2x+3\right)=8\)

\(10x^2+9x-10x^2-13x+3=8\)

\(-4x=8-3\)

\(-4x=5\)

\(x=-\dfrac{5}{4}\)

\(\left(3x-5\right)\left(7-5x\right)+\left(5x+2\right)\left(3x-2\right)-2=0\)

\(-15x^2+46x-35+15x^2-4x-4-2=0\)

\(42x-41=0\)

42x=41

x=\(\dfrac{41}{42}\)

bạn sai ý

Diện tích tam giác nhỏ là : \(\dfrac{3\times3}{2}=4,5\) (\(cm^2\))

Diện tích hình vuông là : \(4,5\times4=18\left(cm^2\right)\)

Dienj tích hình tròn là: \(3,14\times3\times3=28,26\left(cm^2\right)\)

Diện tích phần tô đậm là: 28,26-18=10,26(\(cm^2\))

ĐS...

\(52dm^2< 4m^23dm^2\)

\(\dfrac{1}{2}km^2>500m^2\)

\(\dfrac{\sqrt{x}+1}{\sqrt{x}+3}=\dfrac{1}{2}\)

=> \(2\left(\sqrt{x}+1\right)=\sqrt{x}+3\)

     \(2\sqrt{x}+2=\sqrt{x}+3\)

     \(2\sqrt{x}-\sqrt{x}=3-2\)

     \(\sqrt{x}=1\)

=> x=1

A

\(n+1=n+\dfrac{1}{n}+2\)

\(\dfrac{1}{n}=-1\)

=> 1=-n

     n=-1