tim x de: (x+1)+(x+3)+(x+5)+...+(x+77)+(x+79)=120
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14 tháng 3 2022 lúc 8:04
Tính nhanh :
3/9 x 77/79 + 3/9 x 2/79
3/9 x 77/79 + 3/9 x 2/79
= 3/9 x (77/79 + 2/79)
= 3/9 x 1
= 3/9
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Tim x
a } 120 - ( x + 14 ) = 45
b } 79 - x- 18 = 37
a) 120 - ( x + 14 ) = 45
x + 14 = 120 - 45
x + 14 = 75
x = 75 - 14
x = 61
b) 79 - x - 18 = 37
79 - x = 37 + 18
79 - x = 55
x = 79 - 55
x = 24
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a)120-(x+14)=45
=>x+14=120-45
=>x+14=75
=>x=61
b) tự làm
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a,120-(x+14)=45
x+14=120-45
x+14=75
x=75-14
x=61
Vậy...
b,79-x-18=37
79-x=37-18
79-x=19
x=79-19
x=60
Vậy...
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tim x nguyen de |x+1| + |3+x| +|5+x| = 4x
Do |x + 1| > hoặc = 0; |3 + x| > hoặc = 0; |5 + x| > hoặc = 0
=> 4x > hoặc = 0
=> x > hoặc = 0
Khi x > hoặc = 0 thì |x + 1| + |3 + x| + |5 + x| = (x + 1) + (3 + x) +(5 + x)
=> (x + 1) + (3 + x) + (5 + x) = 4x
=> 3x + 9 = 4x
=> 4x - 3x = 9
=> x = 9
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(1/2 +1/3 + 1/4 +....+1/80) x> 1/79 + 2/78 + 3/77 +...+ 78/2 + 79/1)
=>(1/2+1/3+...+1/80)*x>(1+1/79+1+2/78+...+1+78/2+1)
=>\(x\left(\dfrac{1}{2}+\dfrac{1}{3}+...+\dfrac{1}{80}\right)>\dfrac{80}{80}+\dfrac{80}{79}+...+\dfrac{80}{3}+\dfrac{80}{2}\)
=>x>80
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\(\frac{\sqrt{x}+1}{\sqrt{x}-2}+\frac{2\sqrt{x}}{\sqrt{x}+2}+\frac{2+5\sqrt{x}}{4-x}\)
a,rut gon
b,tim x de p duong
c,tim x de p = -5/2
d,tim x de p thuoc z
e,tim x de p >9/2
1.Tìm x thuoc N de
x^2+2x-5 chia het cho x
2.tim x thuoc N de
x^2+x=132
3.tim x,y de
x^2+xy=5
4.tim a thuoc N de
a)a+10 chia het cho a-1
b)3a-6 chia hết cho 3a
Giúp mink với mink cần giúp rồi mink tick cho nhé
1.x=1;5
2.x=11
3.x=1;y=4
4.a)a=2;12 b)a=1;2
nho h cho minh nha
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1.Tim cac chu so x va y de so 1x8y2 chia het cho 36
2.tim cac gia tri nguyen cua n de phan so A=3.n+2/n-1 co gia tri la so nguyen
3.tim cac chu so x y thoa man
(x-2)^2.(x-3)^2=4
4.tim so tu nhien x biet
(x-5):3/100=20.x/100 +5
Cho biểu thức :B=\(\left(\frac{21}{x^2-9}-\frac{x-4}{3-x}-\frac{x-1}{3+x}\right):\left(1-\frac{1}{x+3}\right)\)
a) Rút gọn B
b) Tim x de B =\(\frac{-3}{5}\)
c)Tim x de B<0
\(B=\left(\frac{21}{\left(x-3\right)\left(x+3\right)}+\frac{\left(x-4\right)\left(x+3\right)}{\left(x-3\right)\left(x+3\right)}-\frac{\left(x-3\right)\left(x-1\right)}{\left(x-3\right)\left(x+3\right)}\right):\frac{x+3-1}{x+3}\)\(=\frac{3x+6}{\left(x-3\right)\left(x+3\right)}.\frac{x+3}{x+2}=\frac{3\left(x+2\right)\left(x+3\right)}{\left(x-3\right)\left(x+3\right)\left(x+2\right)}=\frac{3}{x-3}\)Điều kiện \(x\ne3\) \(\Rightarrow\frac{-3}{5}=\frac{3}{x-3}\Leftrightarrow x-3=-5\Leftrightarrow x=-2\)\(B=\frac{3}{x-3}< 0\Leftrightarrow x-3< 0\Leftrightarrow x< 3\)
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a) B=(\(\frac{21}{x^2-9}\)-\(\frac{x-4}{3-x}\)-\(\frac{x-1}{3+x}\)) : (1-\(\frac{1}{x+3}\)) (ĐK: x khác +-3)
=(\(\frac{21}{\left(x-3\right).\left(x+3\right)}\)+\(\frac{x-4}{x-3}\)-\(\frac{x-1}{x+3}\)) : (1-\(\frac{1}{x+3}\))
=(\(\frac{21+\left(x+4\right).\left(x+3\right)-\left(x-1\right).\left(x-3\right)}{\left(x-3\right).\left(x+3\right)}\):(\(\frac{x+3-1}{x+3}\))
=(\(\frac{3x+6}{\left(x-3\right).\left(x+3\right)}\)) . (\(\frac{x+3}{x+2}\))
=(\(\frac{3.\left(x+2\right)}{\left(x-3\right).\left(x+3\right)}\). \(\frac{x+3}{x+2}\)
=\(\frac{3}{x-3}\)
b) B=\(\frac{3}{x-3}\)=\(\frac{-3}{5}\)
(=) \(\frac{3.5}{x-3}\)=-3
(=) -3.(x-3) = 15
(=) -3x=6
(=) x=-2
vậy x=2 thì B=\(\frac{-3}{5}\)
c) B=\(\frac{3}{x-3}\)<0
(=) 3 < x - 3
(=) -x < - 3 - 3
(=) x > 6
Vậy với x > 6 thì B < 0
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\(B=\left(\frac{21}{x^2-9}-\frac{x-4}{3-x}-\frac{x-1}{x+3}\right):\left(1-\frac{1}{x+3}\right)\)
\(B=\left[\frac{21}{\left(x-3\right)\left(x+3\right)}+\frac{\left(x-4\right)\left(x+3\right)}{\left(x-3\right)\left(x+3\right)}-\frac{\left(x-1\right)\left(x-3\right)}{\left(x+1\right)\left(x+3\right)}\right]\) \(:\left[\frac{x+3-1}{x+3}\right]\)
\(B=\frac{21+x^2-x-12-x^2+4x-3}{\left(x-3\right)\left(x+3\right)}:\frac{x+2}{x+3}\)
\(B=\frac{3x+6}{\left(x-3\right)\left(x+3\right)}.\frac{x+3}{x+2}\)
\(B=\frac{3.\left(x+2\right)}{\left(x-3\right)\left(x+3\right)}.\frac{x+3}{x+2}\)
\(B=\frac{3}{x-3}\)
b) \(B=\frac{-3}{5}\Leftrightarrow\frac{3}{x-3}=\frac{-3}{5}\)
\(\Leftrightarrow-3x+9=15\)
\(\Leftrightarrow-3x=6\)
\(\Leftrightarrow x=-2\)
vậy....
c) \(B< 0\Leftrightarrow\frac{3}{x-3}< 0\)
\(\Leftrightarrow x-3< 0\) vì \(3>0\)
\(\Leftrightarrow x< 3\)
vậy....
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Bai 1:
a) Cho A = 963 + 351 + x voi x thuoc N . Tim dieu kien cua x de A chia het cho 9 , de A khong chia hat cho 9
b) Cho B = 10 + 25 + x + 45 voi x thuoc N . Tim dieu kien cua x De B chia het cho 5 , B khong chia het cho 5
Bai 2 : Tim x thuoc N biet :
a) 1 + 2 + 3 + ..... + n = 325
b) 1 + 3 + 5 +... + ( 2n+1) = 144
c) 2 + 4 + 6 + ... + 2n = 756