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x.8+56+x.4-28=x.3+9+x+4*(1-3)
=>12x+(56-28)=(3x+x)+9+4*(-2)
=>12x+28=4x+9-8=4x+1
=>12x-4x=1-28
8x=-27
x=-27/8
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\(\left(x+9\right)+\left(x-2\right)+\left(x+7\right)+\left(x-4\right)+\left(x+5\right)+\left(x-6\right)+\left(x+3\right)+\left(x-8\right)+\left(x+1\right)=95\)
\(x+9+x-2+x+7+x-4+x+5+x-6+x+3+x-8+x+1=95\)
\(\left(x\times9\right)+\left(9-2+7-4+5-6+3-8+1\right)=95\)
\(x\times9+5=95\)
\(x\times9=95-5\)
\(x\times9=90\)
\(x=90:9\)
\(x=10\)
(x + 9) + (x - 2) + (x + 7) + (x - 4) + (x + 5) + (x - 6) + (x + 3) + (x - 8) + (x + 1) = 95
x + 9 + x - 2 + x + 7 + x - 4 + x + 5 + x - 6 + x + 3 + x - 8 + x + 1
(x + x + x + x + x + x + x + x + x) + (9 - 8 + 7 - 6 + 5 - 4 + 3 - 2 + 1) = 95
9 × x + 5 = 95
9 × x = 95 - 5
9 × x = 90
x = 90 : 9
x = 10
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a) 4/7 x X = 1/5 + 2/3
=> 4/7 x X = 3/15 + 10/15
=> 4/7 x X = 13/15
=> X = 13/15 : 4/7
=> X = 13/15 x 4/7 = 52/105
a ) 4 / 7 x X = 1 / 5 + 2 / 3
= > 4 / 7 x X = 3 / 1 5 + 1 0 / 1 5
= > 4 / 7 x X = 1 3 / 1 5
= > X = 1 3 / 1 5 : 4 / 7
= > X = 1 3 / 1 5 x 4 / 7
= 5 2 / 1 0 5
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\(\dfrac{7}{8}:x=5+\dfrac{1}{2}=\dfrac{10}{2}+\dfrac{1}{2}=\dfrac{11}{2}\Rightarrow x=\dfrac{7}{8}:\dfrac{11}{2}=\dfrac{7}{8}x\dfrac{2}{11}=\dfrac{7}{44}\)
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\(\left(x+9\right)+\left(x-8\right)+\left(x+7\right)+\left(x-6\right)+\left(x+5\right)+\left(x-4\right)+\left(x+3\right)+\left(x-2\right)+\left(x+1\right)=95.9\\ =>x+9+x-8+x+7+x-6+x+5+x-4+x+3+x-2+x+1=855\\ =>\left(x+x+x+x+x+x+x+x+x\right)+\left(9-8+7-6+5-4+3-2+1\right)=855\\ =>9x+5=855\\ =>9x=855-5\\ =>9x=850\\ =>x=\dfrac{850}{9}\)
\(\left(x+9\right)+\left(x-8\right)+...+\left(x-2\right)+\left(x+1\right)\)
\(=x+9+x-8+...+x-2+x+1\)
\(=\left(x+9+x-8\right)+...+\left(x+5\right)+...+\left(x-2+x+1\right)\)
(Ta gộp 4 số vào 1 tổng, riêng (x+5) là ta giữ nguyên)
\(=\left(2x-1\right)+...+\left(x+5\right)+...+\left(2x-1\right)\)
\(=4\left(2x-1\right)+\left(x+5\right)\)
\(=8x-4+x-5\)
\(=9x-9\) (1)
Từ bài toán trên, ta có:
\(\left(x+9\right)+\left(x-8\right)+...+\left(x-2\right)+\left(x+1\right)=95,9\)
Từ (1)
\(\Leftrightarrow9x-9=95,9\)
\(9x=95,9-9\)
\(x=86,9:9\)
\(x=9,6\left(5\right)\)
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a) x + 1/15 = 1/3 - 1/4 = 4/12 - 3/12 = 1/12.
=> x = 1/12 - 1/15 = 5/60 - 4/60 = 1/60.
b) x - 5/12 = 1/3 + 1/4 = 4/12 + 3/12 = 7/12.
=> x = 7/12 + 5/12 = 1
c) x x 2/7 = 3/4 x 4/15 = 1/5
=> x = 1/5 : 2/7 = 1/5 x 7/2 = 7/10
d) x : 3/8 = 4/3 : 3/6 = 4/3 x 2 = 8/3
=> x = 8/3 x 3/8 = 1
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1) 7/8 . x = 9/2
x = 9/2 : 7/8
x = 36/7
x - 1/2 . 1/8 = 2/8
x - 1/16 = 2/8
x = 2/8 - 1/16
x = 3/16
7/8 : x = 1/4
x = 7/8 : 1/4
x = 7/2
( 7/8 - x ) + 1/4 = 3/4
7/8 + x = 3/4 - 1/4
7/8 - x = 1/2
x = 7/8 - 1/2
x = 3/4
2) Nếu bớt chiều dài đi 12cm thì được hình vuông
=> Chiều dài hơn chiều rộng 12cm
Hiệu số phần bằng nhau là:
4 - 3 = 1
Chiều dài là:
12 : 1 x 4 = 48 ( cm )
Chiều rộng là:
48 - 12 = 36 ( cm )
Chu vi là:
( 48 + 36 ) x 2 = 168 ( cm )
Diện tích là:
48 x 36 = 1728 ( cm2 )
7/8 x X=9/2
X=9/2:7/8
X=36/7
x-1/2x1/8=2/8
x-1/16=2/8
x=2/8+1/16
x=5/16
7/8:x=1/4
x=7/8:1/4
x=7/2
(7/8-x)+1/4=3/4
(7/8-x)=3/4-1/4
(7/8-x)=1/2
x=7/8-1/2
x=3/8
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1) (x - 35) - 120 = 0
x - 35 = 120
x = 120 + 35
x = 155
2) 310 - (118 - x) = 217
118 - x = 310 - 217
118 - x = 93
x = 118 - 93
x = 25
3) 156 - (x + 61) = 82
x + 61 = 156 - 82
x + 61 = 74
x = 74 - 61
x = 13
4) 814 - (x - 305) = 712
x - 305 = 814 - 712
x - 305 = 102
x = 102 + 305 = 407
5) 100 - 7 - (x - 5) = 58
x - 5 = 93 - 58
x - 5 = 35
x = 35 + 5 = 40
6) 12(x - 1) : 3 = 43 + 23
4(x - 1) = 72
x - 1 = 18
x = 18 + 1 = 19
7) 24 + 5x = 75 : 73
24 + 5x = 49
5x = 25
x = 25 : 5 = 5
8) 5(x - 1) : 3 = 43 + 23
\(\dfrac{5}{3}\left(x-1\right)=72\)
x - 1 = \(\dfrac{216}{5}\)
x = 221/5
9) 5(x - 4)2 - 7 = 13
5(x - 4)2 = 20
(x - 4)2 = 4
\(\Rightarrow\left[{}\begin{matrix}x-4=2\\x-4=-2\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x=6\\x=2\end{matrix}\right.\)
10) (x + 1) + (x + 2) + ... + (x + 30) = 795
=> (x + x + x + ... + x) + (1 + 2 + 3 +...+ 30) = 795 (1)
Đặt A = 1 + 2 + 3 +...+ 30
Số số hạng trong A là: (30 - 1) : 1 + 1 = 30 (số)
Tổng A bằng : (30 + 1).30 : 2 =465
Thay A = 465 vào (1) , ta được:
30x + 465 = 795
=> 30x =330
=> x =11
1: =>x-35=120
=>x=120+35=155
2: =>118-x=310-217=93
=>x=118-93=25
3: =>x+61=156-82=74
=>x=74-61=13
4: =>x-305=814-712=102
=>x=102+305=407
5: =>93-(x-5)=58
=>x-5=35
=>x=40
6: =>4(x-1)=64+8=72
=>x-1=18
=>x=19
7: =>5x+24=49
=>5x=25
=>x=5
8: =>5(x-1):3=4^3+2^3=64+8=72
=>5(x-1)=216
=>x-1=216/5
=>x=221/5
bằng 4.Mình chắc chắn.
mình cũng đồng ý với kết quả trên.
1/4=3/12.
câu hỏi này thì số 4 là thích hợp nhất vì chỉ có 7-4=3/8+4=12 thôi.