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nhìn công thức đây này \(\sqrt[]{\sqrt{ }\hept{\begin{cases}\\\end{cases}}\frac{ }{ }^{ }_{ }\hept{\begin{cases}\\\\\end{cases}}\hept{\begin{cases}\\\\\end{cases}}\hept{\begin{cases}\\\\\end{cases}}\hept{\begin{cases}\\\end{cases}}\orbr{\begin{cases}\\\end{cases}}}\) xong rồi đó không cần cảm ơn
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A. -36 - x = 63
x = -36 - 63
x = -99
Vậy x = -99
B. 2x - 35 = 15
2x = 15 + 35
2x = 50
x = 50 : 2
x = 25
Vậy x = 25
Nhớ k cho mình nhé!
![](https://rs.olm.vn/images/avt/0.png?1311)
Giải:
\(\dfrac{4}{15}+\dfrac{4}{35}+\dfrac{4}{63}+...+\dfrac{4}{399}=\dfrac{x}{49}\)
\(\dfrac{4}{3.5}+\dfrac{4}{5.7}+\dfrac{4}{7.9}+...+\dfrac{4}{19.21}=\dfrac{x}{49}\)
\(2.\left(\dfrac{2}{3.5}+\dfrac{2}{5.7}+\dfrac{2}{7.9}+...+\dfrac{2}{19.21}\right)=\dfrac{x}{49}\)
\(2.\left(\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{9}+...+\dfrac{1}{19}-\dfrac{1}{21}\right)=\dfrac{x}{49}\)
\(2.\left(\dfrac{1}{3}-\dfrac{1}{21}\right)=\dfrac{x}{49}\)
\(2.\dfrac{2}{7}=\dfrac{x}{49}\)
\(\dfrac{4}{7}=\dfrac{x}{49}\)
\(\Rightarrow x=\dfrac{4.49}{7}=28\)
Chúc bạn học tốt!
\(\dfrac{4}{15}+\dfrac{4}{35}+...+\dfrac{4}{399}=\dfrac{x}{49}\)
2 . \(\dfrac{2}{15}+\dfrac{2}{35}+...+\dfrac{2}{399}=\dfrac{x}{49}\)
2 . \(\dfrac{2}{3.5}+\dfrac{2}{5.7}+...+\dfrac{2}{19.21}=\dfrac{x}{49}\)
2 . ( \(\dfrac{1}{3}-\dfrac{1}{21}\) ) = \(\dfrac{x}{49}\)
2 . \(\dfrac{2}{7}\) = \(\dfrac{x}{49}\)
=> \(\dfrac{4}{7}=\dfrac{x}{49}\)
=> \(\dfrac{21}{49}=\dfrac{x}{49}\)
=> \(x=21\)
Vậy \(x=21\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có : \(\dfrac{4}{15}+\dfrac{4}{35}+\dfrac{4}{63}+...+\dfrac{4}{399}=\dfrac{x}{49}\)
\(\Leftrightarrow2\cdot\left(\dfrac{2}{3.5}+\dfrac{2}{5.7}+\dfrac{2}{7.9}+...+\dfrac{2}{19.21}\right)=\dfrac{x}{49}\)
\(\Leftrightarrow\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+...+\dfrac{1}{19}-\dfrac{1}{21}=\dfrac{x}{98}\)
\(\Leftrightarrow\dfrac{1}{3}-\dfrac{1}{21}=\dfrac{x}{98}\)
\(\Leftrightarrow\dfrac{2}{7}=\dfrac{x}{98}\Rightarrow x=28\)
Vậy $x=28$
![](https://rs.olm.vn/images/avt/0.png?1311)
2x-15=25
2x=25+15
2x=40
x=40:2
x=20
63:x=21
x=63:21
x=3
x-8=96
x=96+8
x=104
120-(x-3)=35
x-3=120-35
x-3=85
x=85+3
x=88
35-5(x-2)=15
5(x-2)=35-15
5(x-2)=20
x-2=20:5
x-2=4
x=4+2
x=6
(x-9)-20=19
x-9=19+20
x-9=39
x=39+9
x=48
2782:(216-x-3)=15
câu này mk thấy đề sai rồi bạn nha
130-30(x-2)=100
30(x-2)=130-100
30(x-2)=30
x-2=30:30
x-2=1
x=1+2
x=3
chúc bạn học tốt nha
ủng hộ mk bằng cach tk nha
a/ 2x -15 = 25
2x = 25 - 15
2x = 10
x = 10 : 2
x = 5
b/ 63 : x =21
x = 63 : 21
x = 3
c/ x - 8 = 96
x = 96 + 8
x =104
d/ 120 - (x - 3) = 65
x - 3 = 65
x - 3 = 120 - 65
x - 3 = 55
x = 55 + 3
x = 58
e/ 35 - 5 (x - 2) = 15
5 (x - 2) = 35 - 15
5 (x - 2) = 20
x - 2 = 20 : 5
x - 2 = 4
x = 4 + 2
x = 6
f/ (x - 9) - 20 = 19
x - 9 = 19 + 20
x - 9 = 39
x = 39 - 9
x = 30
g/ 2782 : (216 - x - 3) = 15 (bài này ra số thập phân bạn nên coi lại)
h/ 130 - 30 (x - 2) = 100
30 (x - 2) = 130 -100
30 (x - 2) = 30
x - 2 = 30 : 30
x - 2 = 1
x = 1 + 2
x =3
![](https://rs.olm.vn/images/avt/0.png?1311)
2x-15=25
2x=25+15
2x=40
x=40:2
x=20
x-8=96
x=96+8
x=104
120-(x-3)=35
x-3=120-35
x-3=85
x=85+3
x=88
35-5(x-2)=15
5(x-2)=35-15
5(x-2)=20
x-2=20:5
x-2=4
x=4+2
x=6
(x-9)-20=19
x-9=19+20
x-9=39
x=39+9
x=48
782:(216-x-3)=15
hik như câu này đề lỗi
130-30(x-2)=10
30(x-2)=130-10
30(x-2)=120
x-2=120:30
x-2=4
x=4+2
x=6
chúc bạn học tốt nha
ủng hộ mk bằng cách tk nha
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{1}{3}+\frac{1}{15}+\frac{1}{35}+...+\frac{1}{63}+...+\frac{1}{\left(x+1\right)\left(x+4\right)}=\frac{199}{400}\)(ĐK \(x\ne-1;-4\))
=> \(\frac{1}{1\cdot3}+\frac{1}{3\cdot5}+\frac{1}{5\cdot7}+\frac{1}{7\cdot9}+...+\frac{1}{\left(x+1\right)\left(x+4\right)}=\frac{199}{400}\)
=> \(\frac{1}{2}\left(\frac{2}{1\cdot3}+\frac{2}{3\cdot5}+\frac{2}{5\cdot7}+\frac{2}{7\cdot9}+...+\frac{2}{\left(x+1\right)\left(x+4\right)}\right)=\frac{199}{400}\)
=> \(\frac{1}{2}\left(1-\frac{1}{x+4}\right)=\frac{199}{400}\)
=> \(1-\frac{1}{x+4}=\frac{199}{400}:\frac{1}{2}=\frac{199}{200}\)
=> \(\frac{1}{x+4}=1-\frac{199}{200}=\frac{1}{200}\)
=> x + 4 = 200 => x = 196(tm)
Ta có
1/3 = 1/1 x 3
1/15 = 1/3 x 5
1/35 = 1/5 x 7
.....
1/(x + 1 ) x ( x + 4 )
\(\Rightarrow\)1 - 1/3 + 1/3 - 1/5 +1/5 - 1/7 +............+ 1/( x + 1 ) - 1/( x + 4) = 199/400
\(\Rightarrow\)1 - 1/( x + 4 ) = 199/400
\(\Rightarrow\)1/(x + 4 ) = 1 - 199/400
\(\Rightarrow\)1/(x + 4 ) = 201/400
còn lại bạn tự làm nha
\(\left(-35\right):63=-15:x\\ \dfrac{-35}{63}=\dfrac{-15}{x}\\ x=\dfrac{-15.63}{-35}=\dfrac{3.\left(-5\right).7.9}{-35}=\dfrac{3.\left(-35\right).9}{-35}=3.9=27\)
(-35) : 63 = -15 : \(x\)
\(x\) = (-15) : [ (-35) : 63]
\(x\) = -15 x \(\dfrac{63}{-35}\)
\(x\) = 27