2x - \(\frac14=\frac{-1}{2}\)
K
Khách
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23 tháng 7 2018
a) \(x+2x+3x+...+100x=-213\)
\(\Rightarrow x.\left(1+2+3+...+100\right)=-213\)
\(\Rightarrow x.5050=-213\Rightarrow x=\frac{-213}{5050}\)
b) \(\frac{1}{2}x-\frac{1}{3}=\frac{1}{4}-4\frac{1}{6}\)
\(\Rightarrow\frac{1}{2}x-\frac{1}{3}=\frac{1}{4}-\frac{25}{6}\)
\(\Rightarrow\frac{1}{2}x-\frac{1}{3}=\frac{-47}{12}\)
\(\Rightarrow\frac{1}{2}x=\frac{-43}{12}\Rightarrow x=\frac{-43}{6}\)
d) \(\frac{x+1}{3}=\frac{x-2}{4}\Rightarrow4\left(x+1\right)=3\left(x-2\right)\Rightarrow4x+4=3x-6\)
\(\Rightarrow4x-3x=-6-4\Rightarrow x=-10\)
c) \(3\left(x-2\right)+2\left(x-1\right)=10\)
\(\Rightarrow3x-6+2x-2=10\)
\(\Rightarrow5x=18\Rightarrow x=\frac{18}{5}\)
23 tháng 7 2018
a) \(x+2x+3x+4x+...+100x=-213\)
\(x.\left(1+2+3+4+...+100\right)=-213\)
\(x.5050=-213\)
\(x=-\frac{213}{5050}\)
b) \(\frac{1}{2}x-\frac{1}{3}=\frac{1}{4}-4\frac{1}{6}\)
\(\frac{1}{2}x-\frac{1}{3}=-\frac{47}{12}\)
\(\frac{1}{2}x=-\frac{43}{12}\)
\(x=\frac{-43}{6}\)
2N
3
LG
LMV gamer
CTVHS
23 tháng 8
\(\frac14-2x=5\)
\(2x=\frac14-5\)
\(2x=\frac{-19}{4}\)
\(x=-\frac{19}{4}:2\)
\(x=\frac{-19}{8}\)
S
subjects
CTVHS
1 tháng 9
\(\begin{cases}y=x+20\left(1\right)\\ \frac{y}{50}-\frac{x}{40}=\frac14\left(2\right)\end{cases}\)
thay (1) vào (2) ta được:
\(\frac{x+20}{50}-\frac{x}{40}=\frac14\)
\(\Leftrightarrow4\left(x+20\right)-5x=50\)
4x + 80 - 5x = 50
-x = -30
⇒ x = 30
⇒ y = 30 + 20 = 50
vậy (x; y) = (30; 50)
20 tháng 5 2018
a)P(x) = x^5 + 7x^4 - 9x^3 - 2x^2 - 1/4x
Q(x) = x^5 + 5x ^ 4 - 2x ^ 3 + 4x^2 - 1/4
b) P(x)+Q(x)
= (x^5 – 2x^2 + 7x^4 – 9x^3 – ¼ x ) + (5x^4 – x^5 + 4x^2 – 2x^3 – 1/4)
= x^5 – 2x^2 + 7x^4 – 9x^3 – ¼ x + 5x^4 – x^5 + 4x^2 – 2x^3 – 1/4
= (x^5 - x^5 ) + ( 7x^4 + 5x^4) + (-2x^3-9x^3) + ( -2x^2 +4x^2) + 1/4x+1/4
= 0 + 12x^4 + -11x^3 + 2x^2 + 1/4x + 1/4
= 12x^4 - 11x^3 + 2x^2 + 1/4x + 1/4
P(x) – Q(x)
= (x^5 – 2x^2 + 7x^4 – 9x^3 – ¼ x ) - (5x^4 – x^5 + 4x^2 – 2x^3 – 1/4)
= x^5 – 2x^2 + 7x^4 – 9x^3 – ¼ x - 5x^4 + x^5 - 4x^2 + 2x^3 + 1/4
=(x^5 + x^5 ) + ( 7x^4 - 5x^4) + (2x^3 - 9x^3) + ( -2x^2 - 4x^2) + 1/4x+1/4
= 2x^5 + 2x^4 + -7x^3 + -6x^2 + 1/4x + 1/4
=2x^5 + 2x^4 - 7x^3 - 6x^2 + 1/4x + 1/4
VH
1
6 tháng 7 2022
\(P=\dfrac{\dfrac{8}{12}-\dfrac{3}{12}+\dfrac{5}{11}}{\dfrac{5}{12}+\dfrac{12}{12}-\dfrac{7}{11}}=\dfrac{\dfrac{5}{12}+\dfrac{5}{11}}{\dfrac{17}{12}-\dfrac{7}{11}}=\dfrac{115}{132}:\dfrac{103}{132}=\dfrac{115}{103}\)
HN
16 tháng 12 2018
\(a,\frac{2x+4}{10}+\frac{2-x}{15}=\frac{\left(2x+4\right).3}{10.3}+\frac{\left(2-x\right).2}{15.2}\)
\(=\frac{6x+12}{30}+\frac{4-2x}{30}=\frac{6x+12+4-2x}{30}=\frac{4x+16}{30}\)
\(=\frac{4.\left(x+4\right)}{30}=\frac{2\left(x+4\right)}{15}\)
\(b,\frac{3x}{10}+\frac{2x-1}{15}+\frac{2-x}{20}=\frac{3x.6}{10.6}+\frac{\left(2x-1\right).4}{15.4}+\frac{\left(2-x\right).3}{20.3}\)
\(=\frac{18x}{60}+\frac{8x-4}{60}+\frac{6-3x}{60}=\frac{18x+8x-4+6-3x}{60}=\frac{23x+2}{60}\)
\(c,\frac{x+1}{2x-2}+\frac{x^2+3}{2-2x^2}=\frac{x+1}{2\left(x-1\right)}+\frac{x^2+3}{2\left(1-x^2\right)}=\frac{x+1}{2\left(x-1\right)}+\frac{-x^2-3}{2\left(x^2-1\right)}\)
\(=\frac{x+1}{2\left(x-1\right)}+\frac{-x^2-3}{2\left(x-1\right)\left(x+1\right)}\)\(=\frac{\left(x+1\right)\left(x+1\right)}{2\left(x-1\right)\left(x+1\right)}+\frac{-x^2-3}{2\left(x-1\right)\left(x+1\right)}\)
\(=\frac{x^2+2x+1-x^2-3}{2\left(x-1\right)\left(x+1\right)}=\frac{2x-2}{2\left(x-1\right)\left(x+1\right)}=\frac{2\left(x-1\right)}{2\left(x-1\right)\left(x+1\right)}\)\(=\frac{1}{x+1}\)
25 tháng 2 2020
1) \(\frac{x+1}{2x-2}+\frac{x^2+3}{2-2x^2}\)
\(=\frac{-4x^2+8x-4}{-4x^3+4x^2+4x-4}\)
\(=\frac{-x^2+2x-1}{-x^3+x^2+x-1}\)
\(=\frac{\left(-x+1\right)\left(x-1\right)}{\left(-x-1\right)\left(x-1\right)\left(x-1\right)}\)
\(=\frac{1}{x+1}\)
2) \(\frac{1-2x}{2x}+\frac{2x}{2x-1}+\frac{1}{2x-4x^2}\)
\(=\frac{-16x^3+16x^2-4x}{-16x^4+16x^3-4x^2}\)
\(=\frac{-16x^2+16x-4}{-16x^3+16x^2-4x}\)
\(=\frac{-4x^2+4x-1}{-4x^3+4x^2-x}\)
\(=\frac{\left(-2x+1\right)\left(2x-1\right)}{x\left(-2x+1\right)\left(2x-1\right)}\)
\(=\frac{1}{x}\)
\(2x-\dfrac{1}{4}=\dfrac{-1}{2}\\ 2x=\dfrac{-1}{2}+\dfrac{1}{4}\\ 2x=-\dfrac{1}{4}\\ x=-\dfrac{1}{4}:2\\ x=-\dfrac{1}{8}\)
2x=-1/2+1/4
2x=-1/4
x=-1/4:2
x=-1/8