5|x+1| / 2 = 90 / |x + 1|
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XC
1
20 tháng 8 2023
1: 90<x<180
=>cosx<0
=>\(cosx=-\sqrt{1-\left(\dfrac{4}{5}\right)^2}=-\dfrac{3}{5}\)
\(sin2x=2\cdot sinx\cdot cosx=2\cdot\dfrac{4}{5}\cdot\dfrac{-3}{5}=\dfrac{-24}{25}\)
\(cos2x=2\cdot cos^2x-1=2\cdot\dfrac{9}{25}-1=-\dfrac{7}{25}\)
\(tan2x=\dfrac{-24}{25}:\dfrac{-7}{25}=\dfrac{24}{7}\)
2: 0<x<90
=>cosx>0
=>\(cosx=\sqrt{1-\left(\dfrac{1}{2}\right)^2}=\dfrac{\sqrt{3}}{2}\)
\(cos2x=2\cdot cos^2x-1=2\cdot\dfrac{3}{4}-1=\dfrac{6}{4}-1=\dfrac{2}{4}=\dfrac{1}{2}\)
VV
1
21 tháng 1 2020
5x.5x+1.5x+2<100.................00:224
Có 24 số 0
53x.51.52<1024:2224
53x.53<524
53x<524:53
53x<521
=>3x=21
x=21:3
x=7\(\in\)N
Vậy x=7
Chúc bn học tốt
17 tháng 10 2020
a) \(\frac{2}{3}x-\frac{2}{5}=\frac{1}{2}x-\frac{1}{3}\)
=> \(\frac{2}{3}x-\frac{2}{5}-\frac{1}{2}x+\frac{1}{3}=0\)
=> \(\left(\frac{2}{3}x-\frac{1}{2}x\right)+\left(-\frac{2}{5}+\frac{1}{3}\right)=0\)
=> \(\frac{1}{6}x-\frac{1}{15}=0\Rightarrow\frac{1}{6}x=\frac{1}{15}\Rightarrow x=\frac{1}{15}:\frac{1}{6}=\frac{1}{15}\cdot6=\frac{2}{5}\)
Vậy x = 2/5
b) \(\frac{1}{3}x+\frac{2}{5}\left(x+1\right)=0\)
=> \(\frac{1}{3}x+\frac{2}{5}x+\frac{2}{5}=0\)
=> \(\frac{11}{15}x+\frac{2}{5}=0\Rightarrow\frac{11}{15}x=-\frac{2}{5}\)
=> \(x=\left(-\frac{2}{5}\right):\frac{11}{15}=\left(-\frac{2}{5}\right)\cdot\frac{15}{11}=-\frac{6}{11}\)
Vậy x = -6/11
c) \(\frac{2}{3}-\frac{1}{3}\left(x-\frac{3}{2}\right)-\frac{1}{2}\left(2x+1\right)=5\)
=> \(\frac{2}{3}-\frac{1}{3}x+\frac{1}{2}-x-\frac{1}{2}=5\)
=> \(\left(\frac{2}{3}+\frac{1}{2}-\frac{1}{2}\right)+\left(-\frac{1}{3}x-x\right)=5\)
=> \(\frac{2}{3}-\frac{4}{3}x=5\)
=> \(\frac{4}{3}x=-\frac{13}{3}\Rightarrow x=\left(-\frac{13}{3}\right):\frac{4}{3}=\left(-\frac{13}{3}\right)\cdot\frac{3}{4}=-\frac{13}{4}\)
Vậy x = -13/4
d) \(\frac{11}{5}-\left(\frac{7}{9}-x\right)\cdot\frac{3}{8}=\frac{61}{90}+\frac{x}{3}\)
=> \(\frac{11}{5}-\frac{3}{8}\left(\frac{7}{9}-x\right)=\frac{61}{90}+\frac{30x}{90}\)
=> \(\frac{11}{5}-\frac{7}{24}+\frac{3}{8}x=\frac{61+30x}{90}\)
=> \(\frac{229}{120}+\frac{3}{8}x=\frac{61+30x}{90}\)
=> \(\frac{229}{120}+\frac{3x}{8}=\frac{61+30x}{90}\)
=> \(\frac{229}{120}+\frac{45x}{120}=\frac{61+30x}{90}\)
=> \(\frac{229+45x}{120}=\frac{61+30x}{90}\)
=> \(\frac{3\left(229+45x\right)}{360}=\frac{4\left(61+30x\right)}{360}\)
=> \(3\left(229+45x\right)=4\left(61+30x\right)\)
=> \(687+135x=244+120x\)
=> \(687+135x-244-120x=0\)
=> \(\left(687-244\right)+\left(135x-120x\right)=0\)
=> \(443+15x=0\)
=> \(15x=-443\Rightarrow x=-\frac{443}{15}\)
Vậy x = -443/15
LT
2
TN
19 tháng 2 2016
a) quá dài
b)<=>x^2+2x+1=90
=>x^2+2x-89=0
áp dụng denta
=>2^2-(-4(1.89))=360
\(\Rightarrow x_{1,2}=\frac{-b+-\sqrt{\Delta}}{2a}=\frac{-2+-\sqrt{360}}{2}\)
=>x=\(+-3\sqrt{10}-1\)
LH
6 tháng 7 2018
Mk trả lời đc nè nguyen hung son :))
A = 1 . 2 + 2 . 3 + 3 . 4 + 4 . 5 + ... + 90 . 100
3A = 1 . 2 . 3 + 2 . 3 . ( 4 - 1 ) + 3 . 4 . ( 5 - 2 ) + .... + 90 . 100 . ( 101 - 98 )
3A = 1 . 2 . 3 + 2 . 3 . 4 - 1 + 3 . 4 . 5 - 2 + ... + 90 . 100 . 101 - 98
3A = 99 . 100 . 101
A = ( 99 . 100 . 101 ) : 3
A = 999900 : 3
A = 333300
Vậy A = 333300
22 tháng 8 2017
câu 1
=> x+1/2+x+1/3+x+1/4-x-1/5-x-1/6=0
=> (x+x+x-x-x)+(1/2+1/3+1/4-1/5-1/6)=0
=> x+43/60=0
=> x = -43/60
câu dưới làm tương tự bạn nhé!
LT
6
30 tháng 3 2020
Trả lời :
( X + 1 ) + ( X + 2 ) + ( X + 3 ) + ( X + 4 ) + ( X + 5 ) = 90
=> ( X + X + X + X + X ) + ( 1 + 2 + 3 + 4 + 5 ) = 90
=> ( X x 5 ) + 15 = 90
=> X x 5 = 90 - 15
=> X x 5 = 75
=> X = 75 : 5
=> X = 15.
Vậy X = 15.
Học tốt nha~
\(\dfrac{5\left|x+1\right|}{2}=\dfrac{90}{\left|x+1\right|}\left(x\ne-1\right)\\ \Rightarrow5\left|x+1\right|^2=90\cdot2=180\\ \Rightarrow\left|x+1\right|^2=36\\ \Rightarrow\left|x+1\right|=6\left(\left|x+1\right|>0\right)\\ \Rightarrow\left[{}\begin{matrix}x+1=6\\x+1=-6\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=5\\x=-7\end{matrix}\right.\)