Toán

Diện tích cần lát gạch là:

(12+5)*2*2,75+12*5=153,5m²

Số viên gạch cần dùng là:

153,5:0,05=3070 viên

Diện tích xung quanh của bể bơi:

\(\left(12+5\right)\cdot2\cdot2,75=93,5\left(m^2\right)\)

Diện tích đáy của bể bơi:

\(12\cdot5=60\left(m^2\right)\)

Diện tích cần lát gạch:

\(60+93,5=153,5\left(m^2\right)\)

Số viên gạch cần dùng:

\(153,5:0,05=3070\) (viên)

`a, 1/2 +x=3/4`

`=> x= 3/4 -1/2`

`=> x= 3/4-2/4`

`=>x= 1/4`

`b, 5/2 -x=1/3`

`=> x= 5/2 -1/3`

`=> x= 15/6 - 2/6`

`=>x= 13/6`

`c, 2 . (1/3 +x)=1/5`

`=> 1/3 +x=1/5:2`

`=> 1/3 +x= 1/10`

`=>x= 1/10-1/3`

`=>x= 3/30 - 10/30`

`=>x=-7/30`

`d, 2/3 - (1/2 -x)=1/5`

`=> 1/2-x= 2/3 -1/5`

`=>1/2-x= 10/15 - 3/15`

`=>1/2-x=7/15`

`=>x= 1/2-7/15`

`=>x=1/30`

`1/2 + x = 3/4`

`=>    x  = 3/4 - 1/2`

`=>    x   = 1/4`

`5/2 - x  = 1/3`

`=>    x  =  5/2 - 1/3`

`=>    x  = 13/6`

`2.(1/3 + x) = 1/5`

`=>1/3 + x  = 1/10 `

`=>         x =  1/10 - 1/3`

`=>        x   = -7/30`

`2/3 - (1/2 -x)= 1/5`

`=>     1/2 - x = 7/15`

`=>             x  = 1/2 - 7/15`

`=>             x  = 1/30`

a. \(\dfrac{1}{2}+x=\dfrac{3}{4}\)

⇔ \(x=\dfrac{3}{4}-\dfrac{1}{2}\)

⇔ \(x=\dfrac{1}{4}\)

b. \(\dfrac{5}{2}-x=\dfrac{1}{3}\)

⇔ \(-x=\dfrac{1}{3}-\dfrac{5}{2}\)

⇔ \(-x=-\dfrac{13}{6}\)

⇔ \(x=\dfrac{13}{6}\)

c. \(2\left(\dfrac{1}{3}+x\right)=\dfrac{1}{5}\)

⇔ \(\dfrac{1}{3}+x=\dfrac{1}{5}\div2\)

⇔ \(x=\dfrac{1}{10}-\dfrac{1}{3}\)

⇔ \(-\dfrac{7}{30}\)

d. \(\dfrac{2}{3}-\left(\dfrac{1}{2}-x\right)=\dfrac{1}{5}\)

⇔ \(-\dfrac{1}{2}+x=\dfrac{1}{5}-\dfrac{2}{3}\)

⇔ \(x=-\dfrac{7}{15}+\dfrac{1}{2}\)

⇔ \(x=\dfrac{1}{30}\)

1: x thuộc Ư(18)

=>x thuộc {1;2;3;6;9;18}

mà x thuộc B(4)

nên xthuộc rỗng

2: x thuộc Ư(20)

=>x thuộc {1;2;4;5;10;20}

mà x thuộc B(2)

nên x thuộc {2;4;10;20}

3: x thuộc B(12)

=>x thuộc {0;12;24;36;48;60;72;..}

mà 30<=x<=100

nên x thuộc {36;48;60;72;84;96}

4: x thuộc Ư(150)

=>x thuộc {1;2;3;5;6;10;15;25;30;50;75;150}

mà x<=50

nên x thuộc {1;2;3;5;6;10;15;25;30;50}

1: =>3^x=81

=>x=4

2: =>2^x=8

=>x=3

3: =>x^3=2^3

=>x=2

4: =>x^20-x=0

=>x(x^19-1)=0

=>x=0 hoặc x=1

5: =>2^x=32

=>x=5

6: =>(2x+1)^3=9^3

=>2x+1=9

=>2x=8

=>x=4

7: =>x^3=115

=>\(x=\sqrt[3]{115}\)

8: =>(2x-15)^5-(2x-15)^3=0

=>(2x-15)^3*[(2x-15)^2-1]=0

=>2x-15=0 hoặc (2x-15)^2-1=0

=>2x-15=0 hoặc 2x-15=1 hoặc 2x-15=-1

=>x=15/2 hoặc x=8 hoặc x=7

1. Tìm số tự nhiên x biết:

1) \(3^x.3=243\)

\(3^x=243:3\)

\(3^x=81\)

\(3^x=3^4\)

\(\Rightarrow x=4\)

_____

2) \(7.2^x=56\)

\(2^x=56:7\)

\(2^x=8\)

\(2^x=2^3\)

\(\Rightarrow x=3\)

_____

3) \(x^3=8\)

\(x^3=2^3\)

\(\Rightarrow x=3\)

_____

4) \(x^{20}=x\)

\(x^{20}-x=0\)

\(x\left(x^{19}-1\right)=0\)

\(\Rightarrow x=0\) hoặc \(x=1\)

5) \(2^x-15=17\)

\(2^x=17+15\)

\(2^x=32\)

\(2^x=2^5\)

\(\Rightarrow x=5\)

_____

6) \(\left(2x+1\right)^3=9.81\)

\(\left(2x+1\right)^3=729=9^3\)

\(\rightarrow2x+1=9\)

\(2x=9-1\)

\(2x=8\)

\(x=8:2\)

\(\Rightarrow x=4\)

_____

7) \(x^6:x^3=125\)

\(x^3=125\)

\(x^3=5^3\)

\(\Rightarrow x=5\)

_____

8) \(\left(2x-15\right)^5=\left(2x-15\right)^3\)

\(\rightarrow\left(2x-15\right)^5-\left(2x-15\right)^3=0\)

\(\left(2x-15\right)^3.\left[\left(2x-15\right)^2-1\right]=0\)

\(\Leftrightarrow\left\{{}\begin{matrix}\left(2x-15\right)^3=0\\\left(2x-15\right)^2-1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{15}{2}\\x=7\\x=8\end{matrix}\right.\)

_____

9) \(3^{x+2}-5.3^x=36\)

\(3^x.\left(3^2-5\right)=36\)

\(3^x.\left(9-5\right)=36\)

\(3^x.4=36\)

\(3^x=36:4\)

\(3^x=9\)

\(3^x=3^2\)

\(\Rightarrow x=2\)

_____

10) \(7.4^{x-1}+4^{x+1}=23\)

\(\rightarrow7.4^{x-1}+4^{x-1}.4^2=23\)

\(4^{x-1}.\left(7+4^2\right)=23\)

\(4^{x-1}.\left(7+16\right)=23\)

\(4^{x-1}.23=23\)

\(4^{x-1}=23:23\)

\(4^{x-1}=1\)

\(4^{x-1}=4^1\)

\(\rightarrow x-1=0\)

\(x=0+1\)

\(\Rightarrow x=1\)

Chúc bạn học tốt

\(=\dfrac{3\left(\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{7}+\dfrac{1}{13}\right)}{11\left(\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{7}+\dfrac{1}{13}\right)}=\dfrac{3}{11}\)

\(\dfrac{0,75-0,6+\dfrac{3}{7}+\dfrac{3}{13}}{2,75-2,2+\dfrac{11}{7}+\dfrac{11}{13}}\\ =\dfrac{\dfrac{3}{4}-\dfrac{3}{5}+\dfrac{3}{7}+\dfrac{3}{13}}{\dfrac{11}{4}-\dfrac{11}{5}+\dfrac{11}{7}+\dfrac{11}{13}}\\ =\dfrac{3\left(\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{7}+\dfrac{1}{13}\right)}{11\left(\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{7}+\dfrac{1}{13}\right)}\\ =\dfrac{3}{11}\)

`a, 1/2 +1/3 +1/4`

`= 6/12 + 4/12 + 3/12`

`= (6+4+3)/12`

`= 13/12`

`b,5/2 -1/3 +1/4`

`= 30/12 - 4/12 + 3/12`

`=(30-4+3)/12`

`= 29/12`

`c, 1/2 . 1/3 +1/2 . 2/3`

`= 1/2. (1/3+2/3)`

`= 1/2. 3/3`

`=1/2 .1`

`=1/2`

`d, 3/2 - 1/3 +2/5`

`= 45/30 - 10/30 + 12/30`

`=(45-10+12)/30`

`= 47/30`

1/² là 1² hả bạn?

Hay sao?

a: 1/2+1/3+1/4

=12/24+8/24+6/24=26/24=13/12

b: 5/2-1/3+1/4

=30/12-4/12+3/12=29/12

c: =1/2(1/3+2/3)=1/2*3/3=1/2

d: =45/30-10/30+12/30

=47/30

Tách ?

`a, 70 -5.(x-3) =45`

`=> 5.(x-3)= 70-45`

`=> 5.(x-3)=25`

`=>x-3=25:5`

`=>x-3=5`

`=>x= 5+3`

`=>x=8`

______

`b,10 + 2.x = 4^5:4^3`

`=> 10 + 2.x = 4^(5-3)`

`=> 10 + 2.x =4^2=16`

`=> 2.x=16-10`

`=>2.x=6`

`=>x=6:2`

`=>x=3`

_____

`c,60-3.x-2=51`

`=>  60-3.x= 51+2`

`=> 60-3.x=53`

`=>3.x=60-53`

`=> 3.x= 7`

`=>x= 7/3`

____

`d, 4.x-20=2^5:2^3`

`=> 4.x-20=2^(5-3)`

`=> 4.x-20=2^2`

`=> 4.x= 4+20`

`=>4.x=24`

`=>x=24:4`

`=>x=6`

____

`2^x . 4=16`

`=> 2^x=16:4`

`=>2^x= 4`

`=>2^x=2^2`

`=>x=2`

____

`f, 3^x . 3=243`

`=>3^x=243:3`

`=> 3^x=81`

`=> 3^x=3^3`

`=>x=3`

_____

`g, 64. 4^x =16^8`

`=> 4^3 . 4^x=(4^2)^8`

`=> 4^3 . 4^x = 4^(16)`

`=> 4^x= 4^(16-3)`

`=>4^x=4^(13)`

`=>x=13`

_____

`2^x . 16^2 =1024`

`=> 2^x= 1024 : 16^2`

`=>2^x=4`

`=>2^x=2^2`

`=>x=2`

a: =>5(x-3)=25

=>x-3=5

=>x=8

b: =>2x=16-10=6

=>x=3

c: =>58-3x=51

=>3x=7

=>x=7/3

d: =>4x-20=4

=>4x=24

=>x=6

e: =>2^x=4

=>2^x=2^2

=>x=2

f: =>3^x=81

=>3^x=3^4

=>x=4

g: =>4^x*4^3=4^16

=>x+3=16

=>x=13

h: =>2^x=1024/256=4=2^2

=>x=2

1: =>x-18=13

=>x=31

2: =>73-x=87-20=67

=>x=6

3: =>x-5=15

=>x=20

4: =>(x+2)^2:3=3

=>(x+2)^2=9

=>x+2=3 hoặc x+2=-3

=>x=1 hoặc x=-5

5: =>2(x-1)^2=18

=>(x-1)^2=9

=>x-1=3 hoặc x-1=-3

=>x=-2 hoặc x=4

6: =>3^x(1/3+1+3)=39

=>3^x=9

=>x=2

1) (x+7)-25=3

=> x + 7= 13+25

=> x + 7= 38

x = 38 - 7

x = 31

2) 87 - ( 73 - x ) = 20

=> 73 - x=87-20

=> 73-x=67

x=73-67

x=6

3) x-105:21=15

=> x-105=15.21

=>x-105=315

x=315+105

x=420

bốn câu kia mình ko thấy rõ

a: góc CAO+góc CNO=90+90=180 độ

=>CAON nội tiếp đường tròn đường kính CO

Tâm là trung điểm của OC