Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
d) 215 + ( x - 21 ) : 2 = 235
215 + ( x - 21 ) = 235 . 2
215 + ( x - 21 ) = 470
x - 21 = 470 - 215
x - 21 = 255
x = 255 + 21
x = 276
các bài còn lại làm tương tự nhé
nó dài lắm mik
nhớ ủng hộ mik nhé
a) \(215+x=400\)
\(\Rightarrow x=400-215\)
\(\Rightarrow x=185\)
b) \(12,5-2x=\dfrac{1}{5}\)
\(\Rightarrow2x=12,5-\dfrac{1}{5}\)
\(\Rightarrow2x=\dfrac{123}{10}\)
\(\Rightarrow x=\dfrac{123}{10}:2\)
\(\Rightarrow x=\dfrac{123}{20}\)
Bài 1:
a) 81 + 243 + 319 = 81 + 319 + 243
= 400 + 243 = 643
b) 168 + 1999 + 132 = 168 + 132 + 1999
= 300 + 1999 = 2299
c) 5.25.74.20.4 = (5.20).(25.4).74
= 100.100.74 = 740 000
d) 32.74 + 32.53 = 32.( 74 + 53 )
= 32.127 = 4064
e) 26 + 27 + 28 + 29 + ... + 34 + 35 = (26 + 34) + (27+33) + (28 + 32) + (29 + 31) + 30 + 35
= 60 x 4 + 30 + 35
= 240 + 30 + 35 = 270 + 35 = 305
g) 1 + 3 + 5 + 7 + ... + 99 + 101 = (1 + 99) + (2 + 98) + ... + (48 + 52) + (49 + 51) + 101
= 100 x 49 + 101
= 490 + 101 = 591
Bài 2:
a) 23 - ( 34 - x ) = 23 b) x - ( 74 + 126 ) = 100
34 - x = 23 - 23 74 + 126 = x - 100
34 - x = 0 200 = x - 100
x = 34 - 0 x = 200 - 100
x = 34 x = 100
c) 2436 : x = 12 d) 317 + ( 146 - x ) = 417
x = 2436 : 12 146 - x = 417 - 317
x = 23 146 -x = 100
x = 146 - 100
x = 46
Mình không có thời gian để làm nốt câu e, mong bạn thông cảm!
a. 23 . ( 42 - x ) = 46
42 - x = 46 : 23
42 - x = 2
x = 42 - 2
x = 40
b. 7x - 8 = 41
7x = 41 + 8
7x = 49
x = 49 : 7
x = 7
c. 125 - 5(x + 3) = 15
5(x + 3) = 125 - 15
5(x + 3) = 110
x + 3 = 110 : 5
x + 3 = 22
x = 22 - 3
x = 19
a) 23 . ( 42 - x) = 46 => 42 - x = 46 : 23 = 2
=> x = 42 - 2 = 40
b) 7x - 8 = 41 => 7x = 41 + 8 = 49 => x = 49 : 7 = 7
c) 125 - 5.(x+3) = 15 => 5.(x+3) = 125 - 15 = 110 => x + 3 = 110 : 5 =22
=> x = 22 - 3 = 19
a)\(\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}+\frac{1}{72}+\frac{1}{90}+x=\frac{3}{5}\)
\(\Rightarrow\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}+\frac{1}{8.9}+\frac{1}{9.10}+x=\frac{3}{5}\)
\(\Rightarrow\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{9}-\frac{1}{10}+x=\frac{3}{5}\)
\(\Rightarrow\frac{1}{2}-\frac{1}{10}+x=\frac{3}{5}\)
\(\Rightarrow\frac{2}{5}+x=\frac{3}{5}\)
\(\Rightarrow x=\frac{3}{5}-\frac{2}{5}=\frac{1}{5}\)
b)\(\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{13.15}+x=\frac{1}{3}\)
\(\Rightarrow\frac{2}{3}-\frac{2}{5}+\frac{2}{5}-\frac{2}{7}+...+\frac{2}{13}-\frac{2}{15}+x=\frac{1}{3}\)
\(\Rightarrow\frac{2}{3}-\frac{2}{15}+x=\frac{1}{3}\)
\(\Rightarrow\frac{8}{15}+x=\frac{1}{3}\)
\(\Rightarrow x=\frac{1}{3}-\frac{8}{15}=-\frac{1}{5}\)
c)\(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{x\left(x+1\right)}=\frac{9}{10}\)
\(\Rightarrow\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{x\left(x+1\right)}=\frac{9}{10}\)
\(\Rightarrow\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{x}-\frac{1}{x+1}=\frac{9}{10}\)
\(\Rightarrow\frac{1}{1}-\frac{1}{x+1}=\frac{9}{10}\)
\(\Leftrightarrow\frac{x+1-1}{x+1}=\frac{9}{10}\)
\(\Rightarrow\frac{x}{x+1}=\frac{9}{10}\)
\(\Rightarrow x=9\)
b) \(\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{13.15}+x=\frac{1}{3}\)
\(\Leftrightarrow\frac{5-3}{3.5}+\frac{7-5}{5.7}+...+\frac{15-13}{13.15}+x=\frac{1}{3}\)
\(\Leftrightarrow\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{13}-\frac{1}{15}+x=\frac{1}{3}\)
\(\Leftrightarrow\frac{1}{3}-\frac{1}{15}+x=\frac{1}{3}\)
\(\Leftrightarrow x=\frac{1}{15}\)
a, (17x-25):8=81-65
(17x-25):8=16
17x-25=16:8
17x-25=2
17x=2+25
17x=27
x=27:17
x=27/17
b,720:[41-(2x-5)]=40
41-(2x-5)=720:40
41-(2x-5)=18
2x-5=41-18
2x-5=23
2x=23+5
2x=28
x=28:2
x=14
c,231-(x-6)=103
x-6=231-103
x-6=128
x=128+6
x=134
XEM LẠI GIÙM MÌNH BẠN NHA!
đề bài: (17x-25):8+65= 81
(17x-25):8=81-65=16
17x-25= 16 . 8= 128
17x = 128+25=153
x = 153:17=9
b, Đề bài 720:[41-(2x-5)]=8.5
720:[41-(2x-5)]=40
41-(2x-5)=720:40=18
2x-5=41-18=23
2x = 23+5=28
x = 28:2= 14
c, 231-(x-6)=1339:13=103
x-6=231-103=128
x= 128 + 6= 134
Đúng thì **** bạn
a) x*1,2+x*1,8=45
x*(1,2+1,8)=45
x*3=45
x=45:3
x=15
b)x*10,8-x*1,8=108
x*(10,8-1,8)=108
x*9=108
x=108:9
x=12
học tốt nha em ^_^
\(a)\)\(x\times1,2+x\times1,8=45\)
\(\Rightarrow\)\(x\times\left(1,2+1,8\right)=45\)
\(\Rightarrow\)\(x\times3=45\)
\(\Rightarrow\)\(x=45\div3\)
\(\Rightarrow\)\(x=15\)
a) 5.(x-20) = 35
(x-20) = 35:5
x-20 = 7
x = 27
b) (x+125) -301 = 56
x+125 -301 = 56
x - 176 = 56
x = 56 +176
x= 232
c) 215 + (x-21):2 = 235
(x-21):2 = 235 - 215
(x-21):2 = 20
x-21 = 20 .2
x-21 = 40
x = 61
d) (x:23 +45) .67 = 8911
(x:23 +45) = 8911 : 67
x:23+45 = 133
x:23 = 133-45
x:23 = 88
x = 88.23
x = 2024
a) 5.(x - 20) = 35
⇒ x - 20 = 35 : 5
⇒ x - 20 = 7
⇒ x = 7 + 20
⇒ x = 27
b) (x + 125) - 301 = 56
⇒ x + 125 = 56 + 301
⇒ x + 125 = 357
⇒ x = 357 - 125
⇒ x = 232
c) 215 + (x - 21) : 2 = 235
⇒ (x - 21) : 2 = 235 - 215
⇒ (x - 21) : 2 = 20
⇒ x - 21 = 20 x 2
⇒ x - 21 = 40
⇒ x = 21 + 40
⇒ x = 61
d) (x : 23 + 45).67 = 8911
⇒ x : 23 + 45 = 8911 : 67
⇒ x : 23 + 45 = 133
⇒ x : 23 = 133 - 45
⇒ x : 23 = 88
⇒ x = 88 x 23
⇒ x = 2024