1) \(CM:\frac{1}{\sqrt{2}}+\frac{1}{\sqrt{3}}+....+\frac{1}{\sqrt{100}}kh\text{ô}ngph\text{ải}l\text{à}s\text{ố}t\text{ự}nhi\text{ê}n\)
Những câu hỏi liên quan
Ttext{ìm} stext{ố}.nguytext{ê}n.dtext{ư}text{ơ}ng.nhtext{ỏ}.nhtext{ất}.thtext{ỏa}.mtext{ãn}:frac{1}{2}stext{ố}.text{đ}text{ó}.ltext{à}.stext{ố}.chtext{ính}.phtext{ư}text{ơ}ng frac{1}{3}stext{ố}.text{đ}text{ó}.ltext{à}.ltext{ập}.phtext{ư}text{ơ}ng.ctext{ủa}.1.stext{ố}.nguytext{ên} frac{1}{5}stext{ố}.text{đ}text{ó}.ltext{à}.ltext{ũy}.thtext{ừa}.5.ctext{ủa}.1.stext{ố.nguytext{ê}n}
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\(T\text{ìm}\) \(s\text{ố}.nguy\text{ê}n.d\text{ư}\text{ơ}ng.nh\text{ỏ}.nh\text{ất}.th\text{ỏa}.m\text{ãn}:\frac{1}{2}s\text{ố}.\text{đ}\text{ó}.l\text{à}.s\text{ố}.ch\text{ính}.ph\text{ư}\text{ơ}ng\) \(\frac{1}{3}s\text{ố}.\text{đ}\text{ó}.l\text{à}.l\text{ập}.ph\text{ư}\text{ơ}ng.c\text{ủa}.1.s\text{ố}.nguy\text{ên}\) \(\)
\(\frac{1}{5}s\text{ố}.\text{đ}\text{ó}.l\text{à}.l\text{ũy}.th\text{ừa}.5.c\text{ủa}.1.s\text{ố.nguy\text{ê}n}\)
Rút gọn :
a.text{3}sqrt{2}text{+ }4sqrt{text{8}}-sqrt{text{1}text{8}}
b.sqrt{text{3}}-frac{text{1}}{text{3}}sqrt{27}text{+ }2sqrt{text{5}07}
c.sqrt{2text{5}a}text{+ }sqrt{49a}-sqrt{text{6}4a}
d.-sqrt{text{3}text{6}b}text{−}frac{text{1}}{text{3}}sqrt{text{5}4b}text{+}frac{text{1}}{text{5}}sqrt{text{1}text{5}0b}
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Rút gọn :
a.\(\text{3}\sqrt{2}\text{+ }4\sqrt{\text{8}}-\sqrt{\text{1}\text{8}}\)
b.\(\sqrt{\text{3}}-\frac{\text{1}}{\text{3}}\sqrt{27}\text{+ }2\sqrt{\text{5}07}\)
c.\(\sqrt{2\text{5}a}\text{+ }\sqrt{49a}-\sqrt{\text{6}4a}\)
d.\(-\sqrt{\text{3}\text{6}b}\text{−}\frac{\text{1}}{\text{3}}\sqrt{\text{5}4b}\text{+}\frac{\text{1}}{\text{5}}\sqrt{\text{1}\text{5}0b}\)
a) Ta có: \(3\sqrt{2}+4\sqrt{8}-\sqrt{18}\)
\(=\sqrt{2}\left(3+4\cdot2-3\right)\)
\(=8\sqrt{2}\)
b) Ta có: \(\sqrt{3}-\frac{1}{3}\sqrt{27}+2\sqrt{507}\)
\(=\sqrt{3}\left(1-\frac{1}{3}\cdot\sqrt{9}+2\cdot\sqrt{169}\right)\)
\(=\sqrt{3}\left(1-1+26\right)\)
\(=26\sqrt{3}\)
c) Ta có: \(\sqrt{25a}+\sqrt{49a}-\sqrt{64a}\)
\(=\sqrt{25}\cdot\sqrt{a}+\sqrt{49}\cdot\sqrt{a}-\sqrt{64}\cdot\sqrt{a}\)
\(=\sqrt{a}\left(5+7-8\right)\)
\(=4\sqrt{a}\)
d) Ta có: \(-\sqrt{36b}-\frac{1}{3}\sqrt{54b}+\frac{1}{5}\sqrt{150b}\)
\(=-\sqrt{6b}\cdot\sqrt{6}-\frac{1}{3}\cdot\sqrt{6b}\cdot\sqrt{9}+\frac{1}{5}\cdot\sqrt{6b}\cdot\sqrt{25}\)
\(=-\sqrt{6b}\left(\sqrt{6}+1-1\right)\)
\(=-\sqrt{6b}\cdot\sqrt{6}=-6\sqrt{b}\)
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\(choP=\left(\frac{\sqrt{x}+1}{\sqrt{x}}-\frac{2}{\sqrt{x}+1}\right):\left(\frac{\sqrt{x}}{2}+\frac{1}{2\sqrt{x}}\right)a;R\text{ú}tg\text{ọ}nP....b;T\text{í}nhPkhiX=3-2\sqrt{2}c;t\text{ì}mX\text{đ}\text{ể}P=1\)
Tìm \(\text{n}\inℕ\), biết :
\(\frac{1}{\sqrt{1}+\sqrt{2}}+\frac{1}{\sqrt{2}+\sqrt{3}}+\frac{1}{\sqrt{3}+\sqrt{4}}+...+\frac{1}{\sqrt{\text{n}-1}+\sqrt{\text{n}}}=11\).
Sau khi ib với Hoàng Nguyễn thì đề bài như sau
Tìm \(n\inℕ\)biết
\(\frac{1}{\sqrt{1}+\sqrt{2}}+\frac{1}{\sqrt{2}+\sqrt{3}}+..+\frac{1}{\sqrt{n-1}+\sqrt{n}}=11\)
ĐKXĐ: n > 1
Ta đi c/m bài toán tổng quát
\(\frac{1}{\sqrt{a-1}+\sqrt{a}}=\frac{\sqrt{a}-\sqrt{a-1}}{\left(\sqrt{a}-\sqrt{a-1}\right)\left(\sqrt{a}+\sqrt{a-1}\right)}\)
\(=\frac{\sqrt{a}-\sqrt{a-1}}{a-a+1}\)
\(=\sqrt{a}-\sqrt{a-1}\)
Áp dụng vào bài toán đc
\(\frac{1}{\sqrt{1}+\sqrt{2}}+\frac{1}{\sqrt{2}+\sqrt{3}}+\frac{1}{\sqrt{3}+\sqrt{4}}+...+\frac{1}{\sqrt{n-1}+\sqrt{n}}=11\)
\(\Leftrightarrow\sqrt{2}-\sqrt{1}+\sqrt{3}-\sqrt{2}+\sqrt{4}-\sqrt{3}+...+\sqrt{n}-\sqrt{n-1}=11\)
\(\Leftrightarrow\sqrt{n-1}-1=11\)
\(\Leftrightarrow\sqrt{n-1}=12\)
\(\Leftrightarrow n-1=144\)
\(\Leftrightarrow n=145\left(TmĐKXĐ\right)\)
Vậy n = 145
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1. CHỨNG MINH ĐẲNG THỨCa. text{[}3+2sqrt{6}-sqrt{33}text{]}cdottext{[}sqrt{22}+sqrt{6}+4text{]}24b. text{[}frac{1}{5-2sqrt{6}}+frac{2}{5+2sqrt{6}}text{]}cdottext{[}15+2sqrt{6}text{]}c.text{[}frac{4}{3}cdotsqrt{3}+sqrt{2}+sqrt{3frac{1}{3}}text{]}cdottext{[}sqrt{1,2}+sqrt{2}-4sqrt{frac{1}{5}}text{]}4d. sqrt{text{[}1-sqrt{1989}text{]}^2}cdotsqrt{1990+2sqrt{1989}}1988e. frac{a-sqrt{ab}+b}{asqrt{a}+bsqrt{b}}-frac{1}{a-b}frac{sqrt{a}-sqrt{b}-1}{a-b}với a0;b0và ane b
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1. CHỨNG MINH ĐẲNG THỨC
a. \(\text{[}3+2\sqrt{6}-\sqrt{33}\text{]}\cdot\text{[}\sqrt{22}+\sqrt{6}+4\text{]}=24\)
b. \(\text{[}\frac{1}{5-2\sqrt{6}}+\frac{2}{5+2\sqrt{6}}\text{]}\cdot\text{[}15+2\sqrt{6}\text{]}\)
c.\(\text{[}\frac{4}{3}\cdot\sqrt{3}+\sqrt{2}+\sqrt{3\frac{1}{3}}\text{]}\cdot\text{[}\sqrt{1,2}+\sqrt{2}-4\sqrt{\frac{1}{5}}\text{]}=4\)
d. \(\sqrt{\text{[}1-\sqrt{1989}\text{]}^2}\cdot\sqrt{1990+2\sqrt{1989}}=1988\)
e. \(\frac{a-\sqrt{ab}+b}{a\sqrt{a}+b\sqrt{b}}-\frac{1}{a-b}=\frac{\sqrt{a}-\sqrt{b}-1}{a-b}\)với \(a>0;b>0\)và \(a\ne b\)
a) \(\left(3+1\sqrt{6}-\sqrt{33}\right)\left(\sqrt{22}+\sqrt{6}+4\right)\)
\(=\sqrt{3}\left(\sqrt{3}+2\sqrt{2}-\sqrt{11}\right).\sqrt{2}\left(\sqrt{11}+\sqrt{3}+2\sqrt{2}\right)\)
\(=\sqrt{6}\left(\sqrt{3}+2\sqrt{2}-\sqrt{11}\right)\left(\sqrt{3}+2\sqrt{2}+\sqrt{11}\right)\)
\(=\sqrt{6}\left[\left(\sqrt{3}+2\sqrt{2}\right)^2-11\right]=\sqrt{6}\left(11+4\sqrt{6}-11\right)=\sqrt{6}.4\sqrt{6}=6.4=24\)
b) \(\left(\frac{1}{5-2\sqrt{6}}+\frac{2}{5+2\sqrt{6}}\right)\left(15+2\sqrt{6}\right)=\left(\frac{5+2\sqrt{6}+10-4\sqrt{6}}{5^2-\left(2\sqrt{6}\right)^2}\right)\left(15+2\sqrt{6}\right)\)
\(=\left(15-2\sqrt{6}\right)\left(15+2\sqrt{6}\right)=15^2-24=201\)
C) \(\left(\frac{4}{3}.\sqrt{3}+\sqrt{2}+\sqrt{3\frac{1}{3}}\right)\left(\sqrt{1,2}+\sqrt{2}-4\sqrt{\frac{1}{5}}\right)\)
\(=\left(\frac{4}{\sqrt{3}}+\frac{\sqrt{6}}{\sqrt{3}}+\frac{\sqrt{10}}{\sqrt{3}}\right)\left(\frac{\sqrt{6}}{\sqrt{5}}+\frac{\sqrt{10}}{\sqrt{5}}-\frac{4}{\sqrt{5}}\right)\)
\(=\frac{1}{\sqrt{15}}\left(\sqrt{6}+\sqrt{10}+4\right)\left(\sqrt{6}+\sqrt{10}-4\right)=\frac{1}{\sqrt{15}}\left[\left(\sqrt{6}+\sqrt{10}\right)^2-16\right]\)
\(=\frac{1}{\sqrt{15}}\left(16+4\sqrt{15}-16\right)=\frac{4\sqrt{15}}{\sqrt{15}}=4\)
d) \(\sqrt{\left(1-\sqrt{1989}\right)^2}.\sqrt{1990+2\sqrt{1989}}=\sqrt{\left(1-\sqrt{1989}\right)^2}.\sqrt{1989+2\sqrt{1989}+1}\)
\(=\sqrt{\left(1-\sqrt{1989}\right)^2}.\sqrt{\left(\sqrt{1989}+1\right)^2}=\left(\sqrt{1989}-1\right)\left(\sqrt{1989}+1\right)=1989-1=1988\)
e) \(\frac{a-\sqrt{ab}+b}{a\sqrt{a}+b\sqrt{b}}-\frac{1}{a-b}=\frac{a-\sqrt{ab}+b}{\left(\sqrt{a}+\sqrt{b}\right)\left(a-\sqrt{ab}+b\right)}-\frac{1}{a-b}=\frac{\sqrt{a}-\sqrt{b}}{\left(\sqrt{a}+\sqrt{b}\right)\left(\sqrt{a}-\sqrt{b}\right)}-\frac{1}{a-b}=\frac{\sqrt{a}-\sqrt{b}-1}{a-b}\)
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\(P=\frac{2x+2}{\sqrt{x}}+\frac{x\sqrt{x}-1}{x-\sqrt{x}}-\frac{x\sqrt{x}+1}{x+\sqrt{x}}a;r\text{ú}tg\text{ọ}nPb;t\text{ì}mGTNNc\text{ủa}Pc;t\text{í}nhPt\text{ạ}ix=12+6\sqrt{3}\)
1. Tính:
a. \(\text{[}\sqrt{ab}+2\sqrt{\frac{b}{a}}-\sqrt{\frac{a}{b}}+\sqrt{\frac{1}{ab}}\text{]}\cdot\sqrt{ab}\)
b.\(\text{[}-\frac{am}{b}\cdot\sqrt{\frac{n}{m}}-\frac{ab}{n}\cdot\sqrt{mn}+\frac{a^2}{b^2}\cdot\sqrt{\frac{m}{n}}\text{]}\cdot\text{[}a^2b^2\cdot\sqrt{\frac{n}{m}}\text{]}\)
a) \(\left(\sqrt{ab}+2\sqrt{\frac{b}{a}}-\sqrt{\frac{a}{b}}+\frac{1}{\sqrt{ab}}\right).\sqrt{ab}\) (ĐK : \(\hept{\begin{cases}a>0\\b>0\end{cases}}\)hoặc \(\hept{\begin{cases}a< 0\\b< 0\end{cases}}\))
\(=ab+2b-a+1\)
b) \(\left(-\frac{am}{b}\sqrt{\frac{n}{m}}-\frac{ab}{n}.\sqrt{mn}+\frac{a^2}{b^2}.\sqrt{\frac{m}{n}}\right)\left(a^2b^2.\sqrt{\frac{n}{m}}\right)\) (ĐK bạn tự xét nhé ^^)
\(=\left(-\frac{a\sqrt{mn}}{b}-\frac{ab\sqrt{m}}{\sqrt{n}}+\frac{a^2}{b^2}.\sqrt{\frac{m}{n}}\right)\left(a^2b^2.\sqrt{\frac{n}{m}}\right)\)
\(=a^2b^2\left(\frac{-an}{b}-ab+\frac{a^2}{b^2}\right)=-a^3bn-a^3b^3+a^4=a^3\left(a-bn-b^3\right)\)
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1.Giải pt sau:(sqrt{2} +2)(xsqrt{2} -1)2xsqrt{2} -sqrt{2}
2.Cho pt: 2(a-1).x-a(x-1)2a+3
3.Giải pt sau:
a) frac{2}{x+frac{text{1}}{text{1}+frac{x+text{1}}{x-2}}}frac{6}{3x-text{1}}
b) frac{frac{x+text{1}}{x-text{1}}-frac{x-text{1}}{x+text{1}}}{text{1}+frac{x+text{1}}{x-text{1}}}frac{x-text{1}}{2left(x+text{1}right)}
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1.Giải pt sau:(\(\sqrt{2}\) +2)(x\(\sqrt{2}\) -1)=2x\(\sqrt{2}\) -\(\sqrt{2}\)
2.Cho pt: 2(a-1).x-a(x-1)=2a+3
3.Giải pt sau:
a) \(\frac{2}{x+\frac{\text{1}}{\text{1}+\frac{x+\text{1}}{x-2}}}=\frac{6}{3x-\text{1}}\)
b) \(\frac{\frac{x+\text{1}}{x-\text{1}}-\frac{x-\text{1}}{x+\text{1}}}{\text{1}+\frac{x+\text{1}}{x-\text{1}}}=\frac{x-\text{1}}{2\left(x+\text{1}\right)}\)
1) Nhìn cái pt hết ham, nhưng bấm nghiệm đẹp v~`~
\(\left(\sqrt{2}+2\right)\left(x\sqrt{2}-1\right)=2x\sqrt{2}-\sqrt{2}\)
\(\Leftrightarrow\left(\sqrt{2}+2\right)\left(x\sqrt{2}-1\right)-2x\sqrt{2}+\sqrt{2}=0\)
\(\Leftrightarrow2x-\sqrt{2}+2x\sqrt{2}-2-2x\sqrt{2}+\sqrt{2}=0\)
\(\Leftrightarrow2x-2=0\Leftrightarrow2x=2\Rightarrow x=1\)
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Mấy bài kia sao cái phương trình dài thê,s giải sao nổi
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1)intsqrt{frac{1-sqrt{x}}{1+sqrt{x}}}dx
2)intfrac{dx}{left(e^x+1right)left(x^2+1right)}
3)intfrac{1+2xsqrt{1-x^2}+2x^2}{1+x+sqrt{1+x^2}}dx
4)intfrac{sin^6x+ctext{os}^6x}{1+6^x}dx
5)int_0^{frac{pi}{2}}frac{sqrt{ctext{os}x}}{sqrt{stext{inx}}+sqrt{ctext{os}x}}dx
6)intfrac{x^4}{2^x+1}dx
7)int_0^{frac{pi^2}{4}}sinsqrt{x}dx
8)intsqrt[6]{1-ctext{os}^3x}.stext{inx}.ctext{os}^5xdx
9)intsqrt{frac{1}{4x}+frac{sqrt{x}+e^x}{sqrt{x}.e^x}}dx
10)intfrac{ctext{os}x+stext{inx}}{left(e^xstext{inx}+1right)...
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1)\(\int\sqrt{\frac{1-\sqrt{x}}{1+\sqrt{x}}}dx\)
2)\(\int\frac{dx}{\left(e^x+1\right)\left(x^2+1\right)}\)
3)\(\int\frac{1+2x\sqrt{1-x^2}+2x^2}{1+x+\sqrt{1+x^2}}\)dx
4)\(\int\frac{sin^6x+c\text{os}^6x}{1+6^x}dx\)
5)\(\int_0^{\frac{\pi}{2}}\frac{\sqrt{c\text{os}x}}{\sqrt{s\text{inx}}+\sqrt{c\text{os}x}}dx\)
6)\(\int\frac{x^4}{2^x+1}dx\)
7)\(\int_0^{\frac{\pi^2}{4}}sin\sqrt{x}dx\)
8)\(\int\sqrt[6]{1-c\text{os}^3x}.s\text{inx}.c\text{os}^5xdx\)
9)\(\int\sqrt{\frac{1}{4x}+\frac{\sqrt{x}+e^x}{\sqrt{x}.e^x}}dx\)
10)\(\int\frac{c\text{os}x+s\text{inx}}{\left(e^xs\text{inx}+1\right)s\text{inx}}dx\)