2x-\(\frac{5}{12}\)=x-\(\frac{1}{2}\)
Ai biết lm giúp mik nha
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20 tháng 7 2017
\(\frac{x}{5}=\frac{20}{x}\)
Ta có :
x . x = 20 . 5
x2 = 100
=> x = 10 hoặc x = -10
25 tháng 3 2019
Rút gọn mỗi số hãng của số ta được :
\(C=\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{99.101}\)
\(=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{99}-\frac{1}{101}\)
\(=1-\frac{1}{101}=\frac{100}{101}\)
Vậy C = 100/101
25 tháng 3 2019
\(C=\frac{4}{1.2.3}+\frac{8}{3.4.5}+\frac{12}{5.6.7}+...+\frac{200}{99.100.101}\)
\(=\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{99.101}\)
\(=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{99}-\frac{1}{101}\)
\(=1-\frac{1}{101}\)
\(=\frac{101}{101}-\frac{1}{101}\)
\(=\frac{100}{101}\)
18 tháng 4 2019
\(a)x+30\%x=-1,31\)
\(\Leftrightarrow x+\frac{3x}{10}=-1,31\)
\(\Leftrightarrow10x+3x=-13,1\)
\(\Leftrightarrow13x=-13,1\Leftrightarrow x=-\frac{131}{130}\)
18 tháng 4 2019
\(b)\left(x-\frac{1}{2}\right):\frac{1}{3}+\frac{5}{7}=9\frac{5}{7}\)
\(\Leftrightarrow\frac{2x-1}{2}.3+\frac{5}{7}=\frac{68}{7}\)
\(\Leftrightarrow\frac{6x-3}{2}=\frac{63}{7}\)
\(\Leftrightarrow\frac{6x-3}{2}=9\)
\(\Leftrightarrow6x-3=18\)
\(\Leftrightarrow x=\frac{7}{2}\)
DD
7 tháng 7 2017
\(a.\)\(\frac{13x-16}{15}+\frac{x-32}{35}< \frac{x-6}{21}\)\(MC:105\)
\(\Leftrightarrow\frac{7\left(13x-16\right)}{105}+\frac{3\left(x-2\right)}{105}< \frac{5\left(x-6\right)}{105}\)
\(\text{Khử mẫu ta dc pt tương đương vs pt:}\)
\(\Leftrightarrow7\left(13x-16\right)+3\left(x-2\right)< 5\left(x-6\right)\)
\(\Leftrightarrow91x-112+3x-6< 5x-30\)
\(\Leftrightarrow94x-118< 5x-30\)
\(\Leftrightarrow94x-5x< 118-30\)
\(\Leftrightarrow89x< 88\)
\(\Leftrightarrow x< \frac{88}{89}\)
.\(b.\)\(\frac{5x+12}{14}+\frac{11x+28}{3}>\frac{4x+9}{17}\)\(MC:714\)
\(\text{Khi khử mẫu pt ta dc pt tương đương}:\):
\(\Leftrightarrow51\left(5x+12\right)+238\left(11x+28\right)>42\left(4x+9\right)\)
\(\Leftrightarrow255x+612+2618x+6664>168x+378\)
\(\Leftrightarrow2873x+7276>168x+378\)
\(\Leftrightarrow2873x-168x>-7276+378\)
\(\Leftrightarrow2705x>-6898\)
\(\Leftrightarrow x>-\frac{6898}{2705}\)
5 tháng 5 2019
1,\(\left(\frac{7}{2}-2x\right).\frac{4}{3}=\frac{22}{3}\)
\(x.\left(\frac{7}{2}-2\right)=\frac{22}{3}:\frac{4}{3}=\frac{22}{3}.\frac{3}{4}=\frac{11}{2}\)
\(x.\frac{3}{2}=\frac{11}{2}\)
\(x=\frac{11}{2}:\frac{3}{2}=\frac{11}{2}.\frac{2}{3}=\frac{11}{3}\)
7 tháng 2 2018
ĐKXĐ : \(\hept{\begin{cases}x^2+x-6\ne0\\x^2+4x+3\ne0\\2x-1\ne0\end{cases}\Leftrightarrow\hept{\begin{cases}\left(x+3\right)\left(x-2\right)\ne0\\\left(x+1\right)\left(x+3\right)\ne0\\x\ne\frac{1}{2}\end{cases}\Rightarrow\hept{\begin{cases}x\ne2;-3\\x\ne-1;-3\\x\ne\frac{1}{2}\end{cases}}}}\)
TXĐ : \(x\ne\left\{-3;-1;\frac{1}{2};2\right\}\)
\(pt\Leftrightarrow\frac{5}{\left(x+3\right)\left(x-2\right)}-\frac{2}{\left(x+1\right)\left(x+3\right)}=\frac{-3}{2x-1}\)
\(\Leftrightarrow\frac{5\left(x+1\right)-2\left(x-2\right)}{\left(x-2\right)\left(x+1\right)\left(x+3\right)}=\frac{-3}{2x-1}\)
\(\Leftrightarrow\frac{3x+9}{\left(x-2\right)\left(x+1\right)\left(x+3\right)}=\frac{-3}{2x-1}\)
\(\Leftrightarrow\frac{3}{\left(x-2\right)\left(x+1\right)}=\frac{-3}{2x-1}\)
\(\Leftrightarrow\frac{1}{x^2-x-2}=\frac{1}{1-2x}\)
\(\Leftrightarrow x^2-x-2-1+2x=0\)
\(\Leftrightarrow x^2+x-3=0\)
\(\Leftrightarrow\left(x^2+2.\frac{1}{2}.x+\frac{1}{4}\right)-\frac{13}{4}=0\)
\(\Leftrightarrow\left(x+\frac{1}{2}\right)^2-\left(\frac{\sqrt{13}}{2}\right)^2=0\)
\(\Leftrightarrow\left(x+\frac{1-\sqrt{13}}{2}\right)\left(x+\frac{1+\sqrt{13}}{2}\right)=0\)
\(\Rightarrow\orbr{\begin{cases}x=\frac{\sqrt{13}-1}{2}\\x=\frac{-\sqrt{13}-1}{2}\end{cases}}\)
BT
7 tháng 2 2018
\(\frac{5}{x^2+x-6}-\frac{2}{x^2+4+3}=-\frac{3}{2x-1}\)
<=> \(\frac{5}{\left(x-2\right)\left(x+3\right)}-\frac{2}{\left(x+1\right)\left(x+3\right)}=-\frac{3}{2x-1}\)
<=> \(\frac{5\left(x+1\right)-2\left(x-2\right)}{\left(x-2\right)\left(x+3\right)}=-\frac{3}{2x-1}\)
<=> \(\frac{5x+5-2x+4}{\left(x-2\right)\left(x+3\right)}=-\frac{3}{2x-1}\)
<=> \(\frac{3x+9}{\left(x-2\right)\left(x+3\right)}=-\frac{3}{2x-1}\)
<=> \(\frac{3\left(x+3\right)}{\left(x-2\right)\left(x+3\right)}=-\frac{3}{2x-1}\)
<=> \(\frac{1}{x-2}=-\frac{1}{2x-1}\)
<=> x-2=1-2x <=> 3x=3
=> x=1
Đáp số: x=1
4 tháng 4 2017
\(\left(3\frac{1}{2}+2x\right).2\frac{2}{3}=5\frac{1}{3}\)
<=>\(\left(\frac{7}{2}+2x\right).\frac{8}{3}=\frac{16}{3}\)
<=>\(\frac{28}{3}+\frac{16x}{3}=\frac{16}{3}\)
<=>\(\frac{16x}{3}=\frac{-2}{3}\)
<=>\(16x=-2\)
<=>\(x=\frac{-1}{8}\)
vậy \(x=\frac{-1}{8}\)
b,\(\left|2x+3\right|=5\)
xét x<0,ta co: \(\left|2x+3\right|=5\)<=> \(-2x+3=5\)<=>\(-2x=2\)<=>\(x=-1\)(loại)
xét x>0,ta co:\(\left|2x+3\right|=5\)<=>\(2x+3=5\)<=>\(2x=2\)<=>\(x=1\)
c,\(\frac{x-2}{4}=\frac{5+x}{3}\)
<=>\(\frac{3x-6}{12}=\frac{20+4x}{12}\)
=>\(3x-6=20+4x\)
<=>\(3x-6-20-4x=0\)
<=>\(-x-26=0\)
<=>\(-x=26\)
<=>\(x=-26\)
kl:.......
10 tháng 2 2017
(\(\frac{1}{4.9}+\frac{1}{9.14}+...+\frac{1}{44.49}\)).\(\frac{1-3-5-...-49}{89}\)
= \(\frac{1}{5}.\left(\frac{5}{4.9}+\frac{5}{9.14}+...+\frac{5}{45.49}\right).\frac{1-3-5-...-49}{89}\)
\(=\frac{1}{5}.\left(\frac{1}{4}-\frac{1}{9}+\frac{1}{9}-\frac{1}{14}+...+\frac{1}{44}-\frac{1}{49}\right).\frac{1-\frac{24.\left(49+3\right)}{2}}{89}\)
\(=\frac{1}{5}.\left(\frac{1}{4}-\frac{1}{49}\right).\left(-7\right)\)
\(=-\frac{9}{28}\)
Có chỗ ghi nhầm 44 thành 45. Tự sửa nhé
10 tháng 2 2017
Bài 2/ a/
|2x + 3| = x + 2
Điều kiện \(x\ge-2\)
Với x < - 1,5 thì ta có
- 2x - 3 = x + 2
<=> 3x = - 5
<=> \(x=-\frac{5}{3}\)
Với \(x\ge-1,5\)thì ta có
2x + 3 = x + 2
<=> x = - 1
\(2x-\frac{5}{12}=x-\frac{1}{2}\)
\(\Leftrightarrow2x-x=-\frac{1}{2}-\frac{5}{12}\)
\(\Leftrightarrow x=-\frac{11}{12}\)
Vậy ...
sr bạn .-. ở trên sai r, mk lm lại :333
\(2x-\frac{5}{12}=x-\frac{1}{2}\)
\(\Leftrightarrow2x-x=-\frac{1}{2}+\frac{5}{12}\)
\(\Leftrightarrow x=-\frac{1}{12}\)
Vậy ..