-7/x = -21/x-34
tìm x
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TT
0
30 tháng 6 2017
\(\frac{7}{\left(x+3\right)\left(x+10\right)}+\frac{11}{\left(x+10\right)+\left(x+21\right)}+\frac{13}{\left(x+21\right)\left(x+34\right)}=\frac{x}{\left(x+3\right)\left(x+34\right)}\)
\(\frac{1}{x+3}-\frac{1}{x+10}+\frac{1}{x+10}-\frac{1}{x+21}+\frac{1}{x+21}-\frac{1}{x+34}=\frac{x}{\left(x+3\right)\left(x+34\right)}\)
\(\frac{1}{x+3}-\frac{1}{x+34}=\frac{x}{\left(x+3\right)\left(x+34\right)}\)
\(\frac{\left(x+34\right)-\left(x+3\right)}{\left(x+3\right)\left(x+34\right)}=\frac{x}{\left(x+3\right)\left(x+34\right)}\)
\(\frac{31}{\left(x+3\right)\left(x+34\right)}=\frac{x}{\left(x+3\right)\left(x+34\right)}\)
\(\Rightarrow x=31\)
KN
16 tháng 8 2020
\(\frac{7}{\left(x+3\right)\left(x+10\right)}+\frac{11}{\left(x+10\right)\left(x+21\right)}+\frac{13}{\left(x+21\right)\left(x+34\right)}=\frac{x}{\left(x+3\right)\left(x+34\right)}\)
\(\Leftrightarrow\frac{1}{x+3}-\frac{1}{x+10}+\frac{1}{x+10}-\frac{1}{x+21}+\frac{1}{x+21}-\frac{1}{x+34}=\frac{x}{\left(x+3\right)\left(x+34\right)}\)
\(\Leftrightarrow\frac{1}{x+3}-\frac{1}{x+34}=\frac{x}{\left(x+3\right)\left(x+34\right)}\)
\(\Leftrightarrow\frac{\left(x+34\right)-\left(x+3\right)}{\left(x+3\right)\left(x+34\right)}=\frac{x}{\left(x+3\right)\left(x+34\right)}\)
\(\Leftrightarrow x+34-x-3=x\)
\(\Leftrightarrow x=31\)
NN
16 tháng 8 2020
\(ĐKXĐ\): \(x\ne-3\); \(x\ne-10\); \(x\ne-21\); \(x\ne-34\)
\(\frac{7}{\left(x+3\right)\left(x+10\right)}+\frac{11}{\left(x+10\right)\left(x+21\right)}+\frac{13}{\left(x+21\right)\left(x+34\right)}=\frac{x}{\left(x+3\right)\left(x+34\right)}\)
\(\Leftrightarrow\frac{1}{x+3}-\frac{1}{x+10}+\frac{1}{x+10}-\frac{1}{x+21}+\frac{1}{x+21}-\frac{1}{x+34}=\frac{x}{\left(x+3\right)\left(x+34\right)}\)
\(\Leftrightarrow\frac{1}{x+3}-\frac{1}{x+34}=\frac{x}{\left(x+3\right)\left(x+34\right)}\)
\(\Leftrightarrow\frac{\left(x+34\right)-\left(x+3\right)}{\left(x+3\right)\left(x+34\right)}=\frac{x}{\left(x+3\right)\left(x+34\right)}\)
\(\Rightarrow\left(x+34\right)-\left(x+3\right)=x\)
\(\Leftrightarrow x+34-x-3=x\)
\(\Leftrightarrow x=31\)( thỏa mãn )
Vậy \(x=31\)
H
3
BT
24 tháng 2 2017
<=> -7(x-34)=-21x <=> -7x+238+21x=0 <=>14x=-238 => x=-17
ĐS: x=-17
24 tháng 2 2017
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mk k biet xin loi ban nha!!!!!
mk k biet xin loi ban nha!!!!!
mk k biet xin loi ban nha!!!!!
VT
1
21 tháng 7 2015
\(\frac{x}{y}=\frac{7}{13}\Rightarrow\frac{x}{7}=\frac{y}{13}\)
Áp dụng tính chất dãy tỉ số bằng nhau ta có :
\(\frac{x}{7}=\frac{y}{13}=\frac{x+y}{7+13}=-\frac{60}{20}=-3\)
Suy ra : \(\frac{x}{7}=-3\Rightarrow x=-3.7=-21\)
\(\frac{y}{13}=-3\Rightarrow y=-3.13=-39\)
vay : x=-21 va y=-39
------------------------------------------------
\(\frac{x}{16}=\frac{y}{21}\Rightarrow\frac{2x}{32}=\frac{y}{21}\)
Áp dụng tính chất dãy tỉ số bằng nhau ta có :
\(\frac{2x}{32}=\frac{y}{21}=\frac{2x-y}{32-21}=\frac{34}{11}=?\)
sai de ko
TT
5 tháng 8 2020
\(\frac{-7}{x}=\frac{-21}{\left(x-34\right)}\)
\(\Leftrightarrow\frac{\left(x-34\right)}{-21}=\frac{x}{-7}\)
\(\Leftrightarrow\frac{\left(x-34\right)}{-21}=\frac{x}{-7}\)
\(\Leftrightarrow\frac{\left(x-34\right)}{-21}=\frac{3x}{-21}\)
\(\Leftrightarrow x-34=3x\)
\(\Leftrightarrow x-3x=34\)
\(\Leftrightarrow x\left(1-3\right)=34\)
\(\Leftrightarrow x\left(-2\right)=34\)
\(\Leftrightarrow x=34:\left(-2\right)=-17\)
20 tháng 9 2020
A) \(\frac{7}{\left(x+3\right)\left(x+10\right)}+\frac{11}{\left(x+10\right)\left(x+21\right)}+\frac{13}{\left(x+21\right)\left(x+34\right)}\)
\(=\frac{\left(x+10\right)-\left(x+3\right)}{\left(x+3\right)\left(x+10\right)}+\frac{\left(x+21\right)-\left(x+10\right)}{\left(x+10\right)\left(x+21\right)}+\frac{\left(x+34\right)-\left(x+21\right)}{\left(x+21\right)\left(x+34\right)}\)
\(=\frac{1}{x+3}-\frac{1}{x+10}+\frac{1}{x+10}-\frac{1}{x+21}+\frac{1}{x+21}-\frac{1}{x+34}\)
\(=\frac{1}{x+3}-\frac{1}{x+34}\)
\(=\frac{\left(x+34\right)-\left(x+3\right)}{\left(x+3\right)\left(x+34\right)}\)\(=\frac{x}{\left(x+3\right)\left(x+34\right)}\)
\(\Rightarrow\left(x+34\right)-\left(x+3\right)=x\)
\(\Rightarrow x=31\)
Vậy, x = 31
20 tháng 9 2020
Bạn áp dụng: \(\frac{k}{x\cdot\left(x+k\right)}=\frac{1}{x}-\frac{1}{x+k}\) với \(x,k\inℝ;x\ne0;x\ne-k\)
Chứng minh: \(\frac{1}{x}-\frac{1}{x+k}=\frac{x+k}{x\left(x+k\right)}-\frac{x}{x\left(x+k\right)}=\frac{x+k-x}{x\left(x+k\right)}=\frac{k}{x\left(x+k\right)}\)
HP
15 tháng 6 2016
a) Dễ thấy VT > 0;mà VT=VP
=>VP > 0 => 4x > 0=> x > 0
=>\(\left|x+\frac{1}{2}\right|=x+\frac{1}{2};\left|x+\frac{1}{3}\right|=x+\frac{1}{3};\left|x+\frac{1}{6}\right|=x+\frac{1}{6}\)
=>BT đầu tương đương \(\left(x+\frac{1}{2}\right)+\left(x+\frac{1}{3}\right)+\left(x+\frac{1}{6}\right)=4x\)
\(=>3x+1=4x=>x=1\)
15 tháng 6 2016
a) Để đẳng thức xảy ra thì: x>0 (vì: \(\left|x+\frac{1}{2}\right|+\left|x+\frac{1}{3}\right|+\left|x+\frac{1}{6}\right|>0\) )
Khi đó: \(\left|x+\frac{1}{2}\right|=x+\frac{1}{2};\left|x+\frac{1}{3}\right|=x+\frac{1}{3};\left|x+\frac{1}{6}\right|=x+\frac{1}{6}\)
=>\(x+\frac{1}{2}+x+\frac{1}{3}+x+\frac{1}{6}=4x\)
<=>x=1
Vậy x=1
b)Điều kiện: \(x\ne-3;-10;-21;-34\)
\(\frac{7}{\left(x+3\right)\left(x+10\right)}+\frac{11}{\left(x+10\right)\left(x+21\right)}+\frac{13}{\left(x+21\right)\left(x+34\right)}=\frac{x}{\left(x+3\right)\left(x+34\right)}\)
<=>\(\frac{1}{x+3}-\frac{1}{x+10}+\frac{1}{x+10}-\frac{1}{x+21}+\frac{1}{x+21}-\frac{1}{x+34}=\frac{x}{\left(x+3\right)\left(x+34\right)}\)
<=>\(\frac{1}{x+3}-\frac{1}{x+34}=\frac{x}{\left(x+3\right)\left(x+34\right)}\)
=>x+34-x-3=x
<=>x=31 (nhận)
Vậy x=31
Y
1
27 tháng 2 2017
Ta có : \(\frac{x+10}{27}=\frac{x}{9}\Leftrightarrow9x+90=27x\)
\(\Rightarrow90=27x-9x\)
\(\Rightarrow90=18x\)
\(\Rightarrow x=90:18=5\)
Vậy x = 5
\(\dfrac{-7}{x}=\dfrac{-21}{x}-34\)
\(\Rightarrow\dfrac{-7}{x}+\dfrac{21}{x}=-34\)
\(\Rightarrow\dfrac{14}{x}=-34\Rightarrow-34x=14\Rightarrow x=\dfrac{-7}{17}\)