tìm x biết
\(\frac{-9}{x}=\frac{-x}{\frac{4}{49}}\)
-7.2.x+3.7.x+2.7=-7.8
\(3^{-1}.3^x+6.3^{x-1}=7.3^6\)
\(25< 5^x:5< 625\)
Những câu hỏi liên quan
Tìm x,y,z:
a) 2.7x+1-3.7x=77
b)\(\frac{x+5}{3}=\frac{27}{x+5}\)
c)\(\frac{2}{3}x=\frac{3}{4}y=\frac{4}{5}zv\text{ã}-y+z=34\)
a,2.7x+1-3.7x=77
=>2.7x.71-3.7x=77
=>7X.(2.7-3)=77
=>7x.11=77
=>7x=7
=>7x=71
=>x=1
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Tìm x biết :
a)\(\frac{3}{2}x-\frac{1}{2}=\frac{2}{5}\) b)\(\frac{4}{5}-\left|x-\frac{2}{3}\right|=\frac{2}{3}\)
c)\(x=\left(2-\frac{15}{7}\right)^2+\left|\frac{-6}{7}\right|+\frac{\sqrt{36}}{49}\)
d)\(x=\frac{16^3.3^{10}+120.6^9}{4^6.3^{12}+6^{11}}\)
Các bn lm nhah giúp mik
thanks
bài 1:Tìm x \(\in\)N,biết:
a)(xn)2=x8(x\(\ne\)0 và x\(\ne\)1)
b)Tìm x:
\(\frac{x^6}{25}\)=625
c)(\(\frac{12}{25}\))x=(\(\frac{5}{3}\))-2-(-\(\frac{3}{5}\))4
1.Tìm x, biết :
|x-1|+|x+3|=3
2.Tìm số nguyên n biết:
a, 25<5^n:5<625
b, 3^4<\(\frac{1}{9}\).•27^n<3^10
| x - 1 | + | x + 3 | = 3 ( * )
xét : x - 1 = 0 => x = 1
x + 3 = 0 => x = -3
x - 1 < 0 => x < 1
x + 3 < 0 => x < -3
x - 1 > 0 => x > 1
x + 3 > 0 => x > -3
Lập bảng xét dấu,ta có :
x -3 1
x+3 - 0 + | +
x-1 - | - 0 +
nếu x < -3 thì * <=> : ( 1 - x ) + ( -3 - x ) = 3
1 - x + ( -3 ) - x = 3
-2x = 5
x = -5/2 ( loại )
nếu -3 \(\le\)x < 1 thì * <=> : ( 1 - x ) + ( x + 3 ) = 3
1 - x + x + 3 = 3
0x = -1 ( ko có GT x thỏa mãn )
nếu x \(\ge\)1 thì * <=> : ( x -1 ) + ( x + 3 ) = 3
x - 1 + x + 3 = 3
2x = 1
x = 1/2 ( ko có GT x thỏa mãn )
Vậy ko có GT x nào thỏa mãn bài trên.
a) 25 < 5n:5 < 625
52 < 5n:5 < 54
2 < n:5 < 4
=> n : 5 = 3
=> n = 15
b) 34 < \(\frac{1}{9}.27^n\)< 310
34 < \(\frac{27^n}{9}\)< 310
34 < 33n-2 < 310
=> 3n - 2 \(\in\) { 5 ; 6 ; 7 ; 8 ; 9 }
Nếu 3n - 2 = 5 thì n = 7/3 ( loại )
Nếu 3n - 2 = 6 thì n = 8/3 ( loại )
Nếu 3n - 2 = 7 thì n = 3 ( thỏa mãn )
Nếu 3n - 2 = 8 thì n = 10/3 ( loại )
Nếu 3n - 2 = 9 thì n = 11/3 ( loại )
Vậy n = 3
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Tìm x biết: \(\frac{x+1}{9}+\frac{x+4}{6}+\frac{x+5}{5}=\frac{x+2}{8}+\frac{x+3}{7}+\frac{x+6}{4}.\)
\(\frac{x+1}{9}+\frac{x+4}{6}+\frac{x+5}{5}=\frac{x+2}{8}+\frac{x+3}{7}+\frac{x+6}{4}\)
\(\Rightarrow\frac{x+1}{9}+\frac{x+4}{6}+\frac{x+5}{5}+3=\frac{x+2}{8}+\frac{x+3}{7}+\frac{x+6}{4}+3\)
\(\Rightarrow\left(\frac{x+1}{9}+1\right)+\left(\frac{x+4}{6}+1\right)+\left(\frac{x+5}{5}+1\right)=\left(\frac{x+2}{8}+1\right)\)\(+\left(\frac{x+3}{7}+1\right)+\left(\frac{x+6}{4}\right)\)
\(\Rightarrow\frac{x+10}{9}+\frac{x+10}{6}+\frac{x+10}{5}=\frac{x+10}{8}+\frac{x+10}{7}+\frac{x+10}{4}\)
\(\Rightarrow\left(x+10\right)\left(\frac{1}{9}+\frac{1}{6}+\frac{1}{5}\right)=\left(x+10\right)\left(\frac{1}{8}+\frac{1}{7}+\frac{1}{4}\right)\)
\(\Rightarrow\left(x+10\right)\frac{43}{90}=\left(x+10\right)\frac{29}{56}\)
\(\Rightarrow x+10=0\)
\(\Rightarrow x=-10\)
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cộng 3 vào cả hai vế nên phương trình vẫn bằng nhau
Ta có \(\frac{x+1}{9}+1+\frac{x+4}{6}+1+\frac{x+5}{5}+1=\frac{x+2}{8}+1+\frac{x+3}{7}+1+\frac{x+6}{4}+1\)
\(\Leftrightarrow\frac{x+10}{9}+\frac{x+10}{6}+\frac{x+10}{5}=\frac{x+10}{8}+\frac{x+10}{7}+\frac{x+10}{4}\)
\(\Leftrightarrow\frac{x+10}{9}+\frac{x+10}{6}+\frac{x+10}{5}-\frac{x+10}{8}-\frac{x+10}{7}-\frac{x+10}{4}=0\)
\(\Leftrightarrow\left(x+10\right)\left(\frac{1}{9}+\frac{1}{6}+\frac{1}{5}-\frac{1}{8}-\frac{1}{7}-\frac{1}{6}\right)=0\)
mà \(\frac{1}{9}+\frac{1}{6}+\frac{1}{5}-\frac{1}{8}-\frac{1}{7}-\frac{1}{6}\ne0\)
\(\Rightarrow x+10=0\)
\(\Leftrightarrow x=-10\)
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Xem thêm câu trả lời
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.
Đọc tiếp
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 x
\(\frac{4-x}{6-x}=\frac{x-3}{x-8}\)
Rút gọn
\(\frac{49^{24}.125^{10}.2^8-5^{30}.7^{49}.4^5}{5^{29}.16^2.7^{48}}\)
Tìm x:
\(\dfrac{4-x}{6-x}\)=\(\dfrac{x-3}{x-8}\)\(\Rightarrow\)(4-x)(x-8)=(6-x)(x-3)
\(\Rightarrow\)12x-x2-32=9x-x2-18
\(\Rightarrow\)3x=14\(\Rightarrow\)x=\(\dfrac{14}{3}\).
\(\dfrac{49^{24}.125^{10}.2^8-5^{30}.7^{49}.4^5}{5^{29}.16^2.7^{48}}\)
=\(\dfrac{7^{48}.5^{30}.2^8-5^{30}.7^{49}.2^{10}}{5^{29}.2^8.7^{48}}\)
=\(\dfrac{7^{48}.5^{30}.2^8.\left(1-7.2^2\right)}{5^{29}.2^8.7^{48}}\)
=5.(1-7.22) = 5.(1-28) = 5.(-27) = -135
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Tính giá trị biểu thức :
a) \(\frac{9}{25}x^2+\frac{12}{35}xy+\frac{4}{49}y^2\) Tại x = 5 ; y =-7
b) \(\frac{25}{16}u^4v^2+\frac{1}{5}u^2v^3+\frac{4}{625}v^4\) Tại u = \(\frac{2}{5}\); v = 5
a,\(=\left(\frac{3}{5}x+\frac{2}{7}y\right)^2=\left(\frac{3}{5}.5+\frac{2}{7}.\left(-7\right)\right)^2=0\)
\(b,=\left(\frac{5}{4}u^2v+\frac{2}{25}v^2\right)^2=\left(\frac{5}{4}.\left(\frac{2}{5}\right)^2.5+\frac{2}{25}.5^2\right)^2=3^2=9\)
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Tìm x,biết:
a) \(\frac{16}{2^x}=1\)
b) \(5^{x+2}=625\)
c) \(\frac{x+3}{8}=\frac{2}{x-3}\)
d) \(\frac{x^2}{6}=\frac{24}{25}\)
a) \(\frac{16}{2^x}=1\Leftrightarrow2^x=16\Leftrightarrow2^x=2^4\Leftrightarrow x=4\)
b)\(5^{x+2}=625\Leftrightarrow5^{x+2}=5^4\Leftrightarrow x+2=4\Leftrightarrow x=2\)
c)\(\frac{x+3}{8}=\frac{2}{x-3}\left(đk:x\ne3\right)\Leftrightarrow\left(x+3\right).\left(x-3\right)=2.8\Leftrightarrow x^2-9=16\Leftrightarrow x^2=25\Leftrightarrow\orbr{\begin{cases}x=5\\x=-5\end{cases}}\)
d)\(\frac{x^2}{6}=\frac{24}{25}\Leftrightarrow25x^2=24.6\Leftrightarrow\left(5x\right)^2=144\Leftrightarrow\orbr{\begin{cases}5x=12\\5x=-12\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=\frac{12}{5}\\x=-\frac{12}{5}\end{cases}}\)
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a) 16=2^x \(\Leftrightarrow\)x=4
b)5^x+2=5^4\(\Leftrightarrow\)x+2=4\(\Leftrightarrow\)x=2
k đi, mk làm tiếp cho
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