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26 tháng 12 2022

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2 tháng 9 2021

\(n=\sqrt{2}\left(\sqrt{3}+1\right)\sqrt{2-\sqrt{3}}\\ n=\left(\sqrt{3}+1\right)\sqrt{4-2\sqrt{3}}\\ n=\left(\sqrt{3}+1\right)\sqrt{\left(\sqrt{3}-1\right)^2}\\ n=\left(\sqrt{3}+1\right)\left|\sqrt{3}-1\right|\\ n=\left(\sqrt{3}+1\right)\left(\sqrt{3}-1\right)\\ n=3-1=2\)

2 tháng 9 2021

nice

14 tháng 11 2021

đề đâu bạn nhỉ?

14 tháng 11 2021

rồi ảnh đâu câu đâu có j đâu mà lm

13 tháng 11 2021

\(26,\\ a,\sin45^0=\cos45^0< \sin50^025'< \sin57^048'=\cos32^012'< \sin72^0=\cos18^0< \sin75^0\\ b,\tan37^026'< \tan47^0< \tan58^0=\cot32^0< \tan63^0< \tan66^019'=\cot23^041'\\ 27,\\ A=\dfrac{\left(\sin^226^0+\sin^264^0\right)+2\left(\cos^215^0+\cos^275^0\right)}{\left(\sin^255^0+\cos^255^0\right)+\left(\sin^242^0+\cos^242^0\right)}-\dfrac{\tan81^0}{2\tan81^0}\\ A=\dfrac{\left(\sin^226^0+\cos^226^0\right)+2\left(\sin^215^0+\cos^215^0\right)}{1+1}-\dfrac{1}{2}\\ A=\dfrac{1+2}{2}-\dfrac{1}{2}=2-\dfrac{1}{2}=\dfrac{3}{2}\)

\(28,\\ \sin^2\alpha=1-\cos^2\alpha=1-\dfrac{1}{2}=\dfrac{1}{2}\\ \Leftrightarrow\sin\alpha=\dfrac{\sqrt{2}}{2}\)

5 tháng 2 2022

Đề bài đâu rồi em?

27 tháng 10 2021

a: \(P=\left(\dfrac{2}{\sqrt{x}-1}+\dfrac{\sqrt{x}}{\sqrt{x}+1}\right)\cdot\dfrac{\sqrt{x}}{x+\sqrt{x}+2}\)

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

\(=\dfrac{\sqrt{x}}{x-1}\)

27 tháng 10 2021

\(P=\left(\dfrac{2}{\sqrt{x}-1}+\dfrac{\sqrt{x}}{\sqrt{x}+1}\right).\dfrac{\sqrt{x}}{x+\sqrt{x}+2}\)

\(\Rightarrow P=\dfrac{2\left(\sqrt{x}+1\right)+\sqrt{x}\left(\sqrt{x}-1\right)}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)}.\dfrac{\sqrt{x}}{x+\sqrt{x}+2}\)

\(\Rightarrow P=\dfrac{x+\sqrt{x}+2}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)}.\dfrac{\sqrt{x}}{x+\sqrt{x}+2}\)

\(\Rightarrow P=\dfrac{\sqrt{x}}{x-1}\)

\(\Rightarrow P=\dfrac{\sqrt{3+2\sqrt{2}}}{3+2\sqrt{2}-1}\)

\(\Rightarrow P=\dfrac{\sqrt{\left(\sqrt{2}+1\right)^2}}{2+2\sqrt{2}}\)

\(\Rightarrow P=\dfrac{\sqrt{2}+1}{2\left(\sqrt{2}+1\right)}\)

\(\Rightarrow P=\dfrac{1}{2}\)

 

5 tháng 2 2022

\(b,\dfrac{\sqrt{12}-\sqrt{6}}{\sqrt{30}-\sqrt{15}}=\dfrac{\sqrt{6}\left(\sqrt{2}-1\right)}{\sqrt{15}\left(\sqrt{2}-1\right)}=\dfrac{\sqrt{6}}{\sqrt{15}}=\dfrac{\sqrt{2}}{\sqrt{5}}\)

\(d,\dfrac{ab-bc}{\sqrt{ab}-\sqrt{bc}}=\dfrac{\left(\sqrt{ab}-\sqrt{bc}\right)\left(\sqrt{ab}+\sqrt{bc}\right)}{\left(\sqrt{ab}-\sqrt{bc}\right)}=\sqrt{ab}+\sqrt{bc}=\sqrt{b}\left(\sqrt{a}+\sqrt{c}\right)\)

\(e,\left(a\sqrt{\dfrac{a}{b}+2\sqrt{ab}}+b\sqrt{\dfrac{a}{b}}\right)\sqrt{ab}\)

\(=a\left(\sqrt{\dfrac{a}{b}+\dfrac{2b.\sqrt{ab}}{b}}+b\sqrt{\dfrac{a}{b}}\right)\sqrt{ab}\)

\(=a\sqrt{a}\sqrt{a+2b\sqrt{ab}}+b\sqrt{a^2}\)

\(=a\sqrt{a^2+2ab\sqrt{ab}}+ab\)

\(=a\left(\sqrt{a^2+2ab\sqrt{ab}}+b\right)\)

\(f,\left(\dfrac{1-a\sqrt{a}}{1-\sqrt{a}}+\sqrt{a}\right)\left(\dfrac{1+a\sqrt{a}}{1+\sqrt{a}}-\sqrt{a}\right)\)

\(=\left(a+\sqrt{a}+1+\sqrt{a}\right)\left(a-\sqrt{a}+1-\sqrt{a}\right)\)

\(=\left(a+2\sqrt{a}+1\right)\left(a-2\sqrt{a}+1\right)\)

\(=\left(\sqrt{a}+1\right)^2\left(\sqrt{a}-1\right)^2\)

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

21 tháng 8 2023

Bài 4:

a) Thay x=49 vào B ta có:

\(B=\dfrac{1-\sqrt{49}}{1+\sqrt{49}}=-\dfrac{3}{4}\)

b) \(A=\left(\dfrac{15-\sqrt{x}}{x-25}+\dfrac{2}{\sqrt{x}+5}\right):\dfrac{\sqrt{x}+1}{\sqrt{x}-5}\)

\(A=\left[\dfrac{15-\sqrt{x}}{\left(\sqrt{x}+5\right)\left(\sqrt{x}-5\right)}+\dfrac{2\left(\sqrt{x}-5\right)}{\left(\sqrt{x}+5\right)\left(\sqrt{x}-5\right)}\right]\cdot\dfrac{\sqrt{x}-5}{\sqrt{x}+1}\)

\(A=\dfrac{15-\sqrt{x}+2\sqrt{x}-10}{\left(\sqrt{x}+5\right)\left(\sqrt{x}-5\right)}\cdot\dfrac{\sqrt{x}-5}{\sqrt{x}+1}\)

\(A=\dfrac{\sqrt{x}+5}{\left(\sqrt{x}+5\right)\left(\sqrt{x}-5\right)}\cdot\dfrac{\sqrt{x}-5}{\sqrt{x}+1}\)

\(A=\dfrac{1}{\sqrt{x}-5}\cdot\dfrac{\sqrt{x}-5}{\sqrt{x}+1}\)

\(A=\dfrac{1}{\sqrt{x}+1}\)

c) Ta có: 

\(M=A-B=\dfrac{1}{\sqrt{x}+1}-\dfrac{1-\sqrt{x}}{\sqrt{x}+1}\)

\(M=\dfrac{1-1+\sqrt{x}}{\sqrt{x}+1}\)

\(M=\dfrac{\sqrt{x}}{\sqrt{x}+1}\)

\(M=\dfrac{\sqrt{x}+1-1}{\sqrt{x}+1}=\dfrac{\sqrt{x}+1}{\sqrt{x}+1}-\dfrac{1}{\sqrt{x}+1}=1-\dfrac{1}{\sqrt{x}+1}\)

Mà M nguyên khi:

\(1\) ⋮ \(\sqrt{x}+1\)

\(\Rightarrow\sqrt{x}+1\in\left\{1;-1\right\}\)

Mà: \(\sqrt{x}+1\ge1\)

\(\Rightarrow\sqrt{x}+1=1\)

\(\Rightarrow\sqrt{x}=0\)

\(\Rightarrow x=0\left(tm\right)\)

Vậy M nguyên khi x=0