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` (x+721) /2020+(x+21) /700+ (x+721)/2021=-1`
`<=>(x+721)/2020+(x+21) /700+ 1+ (x+721)/2021=0`
`<=>(x+721)/2020+(x+721) /700+ (x+721)/2021=0 `
`<=>(x +721) (1/2020+1/700+1/2021 )= 0`
Vì `1/2020+1/700+1/2021>0`
`=>x+721 =0 <=>x=-721`
Vậy `S={-721}`
Ta có: \(\dfrac{x+721}{2020}+\dfrac{x+21}{700}+\dfrac{x+721}{2021}=-1\)
\(\Leftrightarrow\dfrac{x+721}{2020}+\dfrac{x+721}{700}+\dfrac{x+721}{2021}=0\)
\(\Leftrightarrow\left(x+721\right)\left(\dfrac{1}{2020}+\dfrac{1}{700}+\dfrac{1}{2021}\right)=0\)
mà \(\dfrac{1}{2020}+\dfrac{1}{700}+\dfrac{1}{2021}>0\)
nên x+721=0
hay x=-721
Vậy: S={-721}
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\(7x-x=5^{21}:5^{19}+3.2^2-7^0\)
\(6x=5^2+3.2-1\)
\(6x=25+12-1\)
\(6x=36\)
\(x=6\)
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a) – 3 < x < 2 ⇒ x ∈ - 2 ; - 1 ; 0 ; 1
b) − 4 21 < x 21 < 2 21 ⇒ x ∈ - 3 ; - 2 ; - 1 ; 0 ; 1
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Hướng dẫn: áp dụng
a + b = c ⇒ a = c - b và b = c - a
a - b = c ⇒ b = a - c và a = b + c
. . . 21 - 2 3 = 5 21
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a) \(5x+x=39-3^{11}:3^9\)
\(\Leftrightarrow6x=39-3^2\)
\(\Leftrightarrow6x=30\)
\(\Leftrightarrow x=5\)
b) \(2^x:2^5=16\)
\(\Leftrightarrow2^x:2^5=2^4\)
\(\Leftrightarrow2^x=2^4.2^5\)
\(\Leftrightarrow2^x=2^9\)
\(\Leftrightarrow x=9\)
c) \(7x-x=5^{21}:5^{19}+3.2^2-7^0\)
\(\Leftrightarrow6x=5^2+3.4-1\)
\(\Leftrightarrow6x=36\)
\(\Leftrightarrow x=6\)
d) \(7x-2x=6^{17}:6^{15}+44:11\)
\(\Leftrightarrow5x=6^2+4\)
\(\Leftrightarrow5x=40\)
\(\Leftrightarrow x=8\)
a)⇔6x=39-32
⇔6x=30
⇔ x=5
b)2x:25=16
⇔2x=24.25
⇔ 2x=29
⇔ x=9
c)⇔6x=52+3.22-1
⇔ 6x= 36
⇔ x=6
d)⇔5x=62+4
⇔ 5x=40
⇔ x=8
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\(\frac{x+521}{2020}+\frac{x+21}{500}+\frac{x+521}{2021}=-1\)
<=> \(\frac{x+521}{2020}+\left(\frac{x+21}{500}+1\right)+\left(\frac{x+521}{2021}\right)=-1+1\)
=> \(\frac{x+521}{2020}+\frac{x+521}{500}+\frac{x+521}{2021}=0\)
=> \(\left(x+521\right)\left(\frac{1}{2020}+\frac{1}{500}+\frac{1}{2021}\right)=0\)
=> x + 521 = 0 (Vì \(\frac{1}{2020}+\frac{1}{500}+\frac{1}{2021}\ne0\))
=> x = -521