Tìm x \(\in\) N biết :
a)\(8< 2^x\le2^9.2^{-5}\)
b) \(27< 81^3:3^x< 243\)
c)\(\left(\frac{2}{5}\right)^x>\left(\frac{5}{2}\right)^{-3}.\left(\frac{-2}{5}\right)^2\)
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Tìm x ∈ N biết :
a) \(8< 2^x\le2^9.2^{-5}\)
b)\(27< 81^3:3^x< 243\)
c)\(\left(\dfrac{2}{5}\right)^x>\left(\dfrac{5}{2}\right)^{-3}.\left(\dfrac{-3}{5}\right)^2\)
\(a,\Rightarrow2^3< 2^x\le2^4\Rightarrow x=4\\ b,\Rightarrow3^3< 3^{12}:3^x< 3^5\\ \Rightarrow3^3< 3^{12-x}< 3^5\\ \Rightarrow12-x=4\Rightarrow x=8\)
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tìm x thuộc N
a. \(8< 2^x< =2^9.2^{-5}\)
b .27<\(81^3\):\(3^x< 243\)
c . \(\left(\frac{2}{5}\right)^x>\left(\frac{5}{2}\right)^{-3}.\left(\frac{2}{5}\right)^2\)
a) \(8< 2^x\le2^9.2^{-5}\)
\(\Leftrightarrow2^3< x\le2^{9-5}\)
\(\Leftrightarrow2^3< 2^x\le2^4\)
\(\Leftrightarrow3< x\le4\Leftrightarrow x=4\)
b) \(27< 81^3:3^x< 243\)
\(\Leftrightarrow3^2< \left(3^4\right)^3:3^x< 3^5\)
\(\Leftrightarrow3^2< 3^{12}:3^x< 3^5\)
\(\Leftrightarrow3^2< 3^{12-x}< 3^5\)
\(\Leftrightarrow2< 12-x< 5\)
\(\Leftrightarrow\hept{\begin{cases}x=8\\x=9\end{cases}}\)
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bài 1: Tìm x,y biết rằng: x+(-frac{31}{12})^2left(frac{49}{12}right)^2-xy^2 bài 2: tìm x biết:a.5^x.left(5^3right)^2625 b.left(frac{12}{25}right)^xleft(frac{5}{3}right)^{-2}-left(-frac{3}{5}right)^4 c.left(-frac{3}{4}right)^{3x-1}frac{256}{81} d.172x^2-7^9:98^32^{-3}Bài 3: Tìm x varepsilonN biết:a.8 2^xle2^9times2^{-5} b.27 81^3:3^x 243 left(frac{2}{5}right)^xleft(frac{5}{2}right)^{-3}timesleft(-frac{2}{5}right)^2c.
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bài 1: Tìm x,y biết rằng:
\(x+(-\frac{31}{12})^2=\left(\frac{49}{12}\right)^2-x=y^2\)
bài 2: tìm x biết:
a.\(5^x.\left(5^3\right)^2=625\) b.\(\left(\frac{12}{25}\right)^x=\left(\frac{5}{3}\right)^{-2}-\left(-\frac{3}{5}\right)^4\) c.\(\left(-\frac{3}{4}\right)^{3x-1}=\frac{256}{81}\)
d.\(172x^2-7^9:98^3=2^{-3}\)
Bài 3: Tìm x \(\varepsilon\)N biết:
a.\(8< 2^x\le2^9\times2^{-5}\) b.\(27< 81^3:3^x< 243\) \(\left(\frac{2}{5}\right)^x>\left(\frac{5}{2}\right)^{-3}\times\left(-\frac{2}{5}\right)^2\)c.
Bài 1:
Ta có: \(x+\left(-\frac{31}{12}\right)^2=\left(\frac{49}{12}\right)^2-x\)
\(\Leftrightarrow2x=\frac{1440}{144}=10\)
\(\Rightarrow x=5\)
Khi đó: \(y^2=\left(\frac{49}{12}\right)^2-5=\frac{1681}{144}\)
=> \(\hept{\begin{cases}y=\frac{41}{12}\\y=-\frac{41}{12}\end{cases}}\)
Tìm số tự nhiên x biết:
a, \(8< 2^x< \frac{2^9}{2^5}\)
b, \(27< 81^3:3^x< 243\)
c, \(\left(\frac{2}{5}\right)^x>\left(\frac{2}{5}\right)^3.\left(-\frac{2}{5}\right)^2\)
CÁC BN GIẢI HỘ MK NHA!!!! *-**.**=*
Rút gọn: a)\(\frac{2^{19}.27^3+15.4^9.9^4}{6^9.2^{10}.12^{10}}\)
b)\(\frac{\left(-\frac{1}{2}\right)^3-\left(\frac{3}{4}\right)^3.\left(-2\right)^2}{2.\left(-1\right)^5+\left(\frac{3}{4}\right)^2-\frac{3}{8}}\)
Tìm x
a)\(3^{x+1}=9^x\)
b)\(2^{3x+2}=4^{x+5}\)
c)\(3^{2x-1}=243\)
bài1: tìm x:a)8 2^x 2^9.2^5b)27 81^3:3^x 243c)left(frac{2}{5}right)^xleft(frac{5}{2}right)^{-3}.left(frac{-2}{5}right)^2d)left(5x+1right)^2frac{36}{49}e)left(x-frac{2}{9}right)^3left(frac{2}{3}right)^6 f)left(8x-1right)^{2n+1}5^{2n+1}(n thuộc N)bài 2:tìm x,y biết:a)x^2+left(y-frac{1}{10}right)^40b)left(frac{1}{2}x-5right)^{20}+left(y^2-frac{1}{4}right)^{10} 6c)left(x-7right)^{x+1}-left(x-yright)^{x+11}0bài 3:tìm giá trị nhỏ nhất:Aleft(2x+frac{1}{3}right)^2-1tìm Gía...
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bài1: tìm x:
a)\(8< 2^x< =2^9.2^5\)
b)\(27< 81^3:3^x< 243\)
c)\(\left(\frac{2}{5}\right)^x\left(\frac{5}{2}\right)^{-3}.\left(\frac{-2}{5}\right)^2\)
d)\(\left(5x+1\right)^2=\frac{36}{49}\)
e)\(\left(x-\frac{2}{9}\right)^3=\left(\frac{2}{3}\right)^6\) f)\(\left(8x-1\right)^{2n+1}=5^{2n+1}\)(n thuộc N)
bài 2:tìm x,y biết:
a)\(x^2+\left(y-\frac{1}{10}\right)^4=0\)
b)\(\left(\frac{1}{2}x-5\right)^{20}+\left(y^2-\frac{1}{4}\right)^{10}< =6\)
c)\(\left(x-7\right)^{x+1}-\left(x-y\right)^{x+11}=0\)
bài 3:tìm giá trị nhỏ nhất:
\(A=\left(2x+\frac{1}{3}\right)^2-1\)
tìm Gía trị lớn nhất :\(B=-\left(\frac{4}{9}x-\frac{2}{15}\right)^6+3\)
baif4: tìm x,y:
\(x.\left(x-y\right)=\frac{1}{10}\) \(\)
giúp mình với nhé
1.
a) \(x\in\left\{4;5;6;7;8;9;10;11;12;13\right\}\)
b) x=0
d) \(x=\frac{-1}{35}\) hoặc \(x=\frac{-13}{35}\)
e) \(x=\frac{2}{3}\)
CÁC BÀI TẬP VỀ LŨY THỪA SỐ HỮU TỈ
Tìm số hữu tỉ x biết:
a, \(8< 2^x< \frac{2^9}{2^5}\)
b, \(27< 81^3:3^x< 243\)
c, \(\left(\frac{2}{5}\right)^x>\left(\frac{2}{5}\right)^3.\left(-\frac{2}{5}\right)^2\) CÁC BN NHỚ GIẢI THEO CÁCH CỦA LỚP 7 NHÉ!!! =^.^=
Tìm x biết
\(|x+\frac{1}{3}|+\frac{4}{5}=|\left(-3,2\right)+\frac{2}{5}|+\left(27-\frac{3}{5}\right)\left(27-\frac{3^2}{6}\right)\left(27-\frac{3^3}{7}\right)...\left(27-\frac{3^{2010}}{2014}\right)\)
\(\left|x+\frac{1}{3}\right|+\frac{4}{5}=\left|-3,2+\frac{2}{5}\right|+\left(27-\frac{3}{5}\right)\left(27-\frac{3^2}{6}\right)...\left(27-\frac{3^5}{9}\right)...\left(27-\frac{3^{2010}}{2014}\right)\)
\(\Leftrightarrow\left|x+\frac{1}{3}\right|+\frac{4}{5}=\frac{14}{5}+\left(27-\frac{3^2}{6}\right)\left(27-\frac{3^3}{7}\right)...\left(27-27\right)...\left(27-\frac{3^{2010}}{2014}\right)\)
\(\Leftrightarrow\left|x+\frac{1}{3}\right|+\frac{4}{5}=\frac{14}{5}\)
\(\Leftrightarrow\left|x+\frac{1}{3}\right|=2\)
\(\Rightarrow\hept{\begin{cases}x+\frac{1}{3}=2\\x+\frac{1}{3}=-2\end{cases}\Rightarrow\hept{\begin{cases}x=\frac{5}{3}\\x=-\frac{7}{3}\end{cases}}}\)
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bạn ơi, có một chỗ chưa chuẩn .bạn kiểm tra lại giú mình. chỗ vế trái bạn thiếu \(\left(27-\frac{3}{5}\right)\). bạn bổ sung vào cho đúng nhé. dù sao vẫn cảm ơn bạn.
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Tìm x:a) dfrac{2}{3}+left(x-dfrac{1}{2}right)^3dfrac{19}{27}b) left(dfrac{3}{2}right)^{2x-1}:left(dfrac{27}{8}right)^3dfrac{81}{16}c) dfrac{1}{2}.2^x+4.2^x9.2^5d) text{12 - (2x +1)}^2-69
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Tìm x:
\(a\)) \(\dfrac{2}{3}+\left(x-\dfrac{1}{2}\right)^3=\dfrac{19}{27}\)
\(b\)) \(\left(\dfrac{3}{2}\right)^{2x-1}:\left(\dfrac{27}{8}\right)^3=\dfrac{81}{16}\)
\(c\)) \(\dfrac{1}{2}.2^x+4.2^x=9.2^5\)
\(d\)) \(\text{12 - (2x +1)}^2=-69\)
\(a,\Rightarrow\left(x-\dfrac{1}{2}\right)^3=\dfrac{1}{27}=\left(\dfrac{1}{3}\right)^3\\ \Rightarrow x-\dfrac{1}{2}=\dfrac{1}{3}\Rightarrow x=\dfrac{5}{6}\\ b,\Rightarrow\left(\dfrac{3}{2}\right)^{2x-1}:\left(\dfrac{3}{2}\right)^9=\left(\dfrac{3}{2}\right)^4\\ \Rightarrow2x-1-9=4\\ \Rightarrow2x=14\Rightarrow x=7\\ c,\Rightarrow2^{x-1}+2^{x+2}=9\cdot2^5\\ \Rightarrow2^{x-1}\left(1+2^3\right)=9\cdot2^5\\ \Rightarrow2^{x-1}\cdot9=9\cdot2^5\\ \Rightarrow2^{x-1}=2^5\Rightarrow x-1=5\Rightarrow x=6\\ d,\Rightarrow\left(2x+1\right)^2=12+69=81\\ \Rightarrow\left[{}\begin{matrix}2x+1=9\\2x+1=-9\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=4\\x=-5\end{matrix}\right.\)
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\(a,\dfrac{2}{3}+\left(x-\dfrac{1}{2}\right)^3=\dfrac{19}{27}\)
\(\left(x-\dfrac{1}{2}\right)^3=\dfrac{19}{27}-\dfrac{2}{3}\)
\(\left(x-\dfrac{1}{2}\right)^3=\dfrac{1}{27}\)
\(\Rightarrow\left(x-\dfrac{1}{2}\right)^3=\left(\dfrac{1}{3}\right)^3\)
\(\Rightarrow x-\dfrac{1}{2}=\dfrac{1}{3}\)
\(x=\dfrac{1}{2}+\dfrac{1}{3}\)
\(x=\dfrac{1}{5}\)
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