a: =>31-x=60

=>x=-29

b: =>(x-140):35=280-270=10

=>x-140=350

=>x=490

c: =>(1900-2x):35=48

=>1900-2x=1680

=>2x=220

=>x=110

d: =>\(2^{2x-1}=2^9\cdot2=2^{11}\)

=>2x-1=11

=>x=6

e: =>(x+2)^5=4^5

=>x+2=4

=>x=2

f: =>3x-4=0 hoặc x-1=0

=>x=4/3 hoặc x=1

g: =>(2x-1)^2=49

=>2x-1=7 hoặc 2x-1=-7

=>x=-3 hoặc x=4

h: =>x(x+1)/2=78

=>x(x+1)=156

=>x=12

Tìm x:

\(a.\dfrac{35}{28}-x=\dfrac{5}{14}\\ x=\dfrac{35}{28}-\dfrac{5}{14}\\ x=\dfrac{25}{28}\\ b.\dfrac{6}{7}\times x=\dfrac{2}{3}\\ x=\dfrac{2}{3}:\dfrac{6}{7}\\ x=\dfrac{7}{9}\\ c.x\times7=\dfrac{3}{4}\\ x=\dfrac{3}{4}:7\\ x=\dfrac{3}{28}\\ d.2:x-\dfrac{1}{3}=\dfrac{2}{5}\\ 2:x=\dfrac{2}{5}+\dfrac{1}{3}\\ 2:x=\dfrac{11}{15}\\ x=2:\dfrac{11}{15}\\ x=\dfrac{30}{11}.\)

\(a,\dfrac{35}{28}-x=\dfrac{5}{14}\)

\(x=\dfrac{35}{28}-\dfrac{5}{14}\)

\(x=\dfrac{25}{28}\)

\(b,\dfrac{6}{7}\times x=\dfrac{2}{3}\)

\(x=\dfrac{2}{3}:\dfrac{6}{7}\)

\(x=\dfrac{7}{9}\)

\(c,x\times7=\dfrac{3}{4}\)

\(x=\dfrac{3}{4}:7\)

\(x=\dfrac{3}{28}\)

\(d,2:x-\dfrac{1}{3}=\dfrac{2}{5}\)

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

\(2:x=\dfrac{11}{15}\)

\(x=2:\dfrac{11}{15}\)

\(x=\dfrac{30}{11}\)

#YVA

a ; 29 x 64 +116 x 34 

= 29  x 2 x 32 + 116 : 2 x 2 x 34 

= 58 x 32 + 58 x 68 

= 58 ( 32 + 68)

= 58 x 100 

= 5800

b, 136 x 68 + 16 x 272 

=  136 x 68 + 16 x 2 x 136

= 136 x 68 + 136 x 32

= 136 ( 68 + 32)

= 136 x 100

= 13600

\(a,2.\left(x+15\right)-5=35\)

\(\Leftrightarrow2.\left(x+15\right)=35+5\)

\(\Leftrightarrow2.\left(x+15\right)=40\)

\(\Leftrightarrow x+15=40:2\)

\(\Leftrightarrow x+15=20\)

\(\Leftrightarrow x=20-15\)

\(\Leftrightarrow x=5\) \(\text{Vậy }x=5\)

\(b,9x-33=3^{2015}:3^{2014}\)

\(\Leftrightarrow9x-33=3^{2015-2014}\)

\(\Leftrightarrow9x-33=3\)

\(\Leftrightarrow9x=3+33\)

\(\Leftrightarrow9x=36\)

\(\Leftrightarrow x=36:9\)

\(\Leftrightarrow x=4\) \(\text{Vậy }x=4\)

\(c,3.\left(2x-4\right)^3=24\)

\(\Leftrightarrow\left(2x-4\right)^3=24:3\)

\(\Leftrightarrow\left(2x-4\right)^3=8\)

\(\Leftrightarrow\left(2x-4\right)^3=2^3\)

\(\Leftrightarrow2x-4=2\)

\(\Leftrightarrow2x=2+4\)

\(\Leftrightarrow2x=6\)

\(\Leftrightarrow x=6:2\)

\(\Leftrightarrow x=3\) \(\text{Vậy }x=3\)

\(d,\left(x-140\right):7=3\)

\(\Leftrightarrow\left(x-140\right)=3.7\)

\(\Leftrightarrow x-140=21\)

\(\Leftrightarrow x=21+140\)

\(\Leftrightarrow x=161\) \(\text{Vậy }x=161\)

\(e,2.3^x-5^3:5^5=29\)

\(\Leftrightarrow2.3^x-5^3:5^3:5^2=29\)

\(\Leftrightarrow2.3^x-1:5^2=29\)

\(\Leftrightarrow2.3^x-\frac{1}{25}=29\)

\(\Leftrightarrow2.3^x=29+\frac{1}{25}\)

\(\Leftrightarrow2.3^x=\frac{726}{25}\)

\(\Leftrightarrow3^x=\frac{726}{25}:2\)

\(\Leftrightarrow3^x=\frac{726}{25}:2\)

\(\Leftrightarrow3^x=\frac{363}{25}\)

\(\Leftrightarrow3^x=3^{2,435369636...}\)

\(\Leftrightarrow x=2,435369636...\)

\(\text{Vậy }x=2,435369636\left(\text{bạn thử kiểm tra lại đề nha}\right)\)

\(f,12:x\text{ và }x\le5\)

\(\text{Do }x\le5\)

\(\Leftrightarrow12:x\le2,4\left(\text{lấy 12 chia cho cả 2 vế}\right)\)

\(\text{Câu này bạn phải cho điều kiện }x\in N,\text{nếu không x có nhiều giá trị lắm }\)

\(\text{Nếu }x\in N\Rightarrow12:x\in N\)

\(\Leftrightarrow12:x\le2,4\left(\text{lấy 12 chia cho cả 2 vế}\right)\)

\(\Rightarrow12:x\in\left\{0;1;2\right\}\)

\(\begin{matrix}12:x&0&1&2\\x&x\in\varnothing&12&6\\\text{Đánh giá}&Loại&Chọn&Chọn\end{matrix}\)

\(\text{Vậy }x\in\left\{6;12\right\}\)

\(g,3x-2x+7x=16\)

\(\Leftrightarrow x.\left(3-2+7\right)=16\)

\(\Leftrightarrow x.8=16\)

\(\Leftrightarrow x=16:8\)

\(\Leftrightarrow x=2\) \(\text{Vậy }x=2\)

\(h,5^{10}.\left(2x-1\right)=5^{12}\)

\(\Leftrightarrow2x-1=5^{12}:5^{10}\)

\(\Leftrightarrow2x-1=5^2\)

\(\Leftrightarrow2x-1=25\)

\(\Leftrightarrow2x=25+1\)

\(\Leftrightarrow2x=26\)

\(\Leftrightarrow x=26:2\)

\(\Leftrightarrow x=13\) \(\text{Vậy }x=13\)

\(i,5⋮\left(x+1\right)\)

\(\Rightarrow x+1\inƯ\left(5\right)=\left\{-1;1;-5;5\right\}\)

\(\text{Vậy }x\in\left\{-6;-2;0;4\right\}\)

a: =>x+7/4=6:2/3=9

=>x=29/4

b: =>x:5/3=7/5

=>x=7/5*5/3=7/3

c:=>x+1/6=5/3

=>x=10/6-1/6=3/2

d: =>x+4/5=4/5+3/7+3/5

=>x=3/7+3/5=36/35

e: =>x/35=4/5-5/7=3/35

=>x=3

f: =>13/28+x=1/2

=>x=1/28

g: =>1/3-x=1/9

=>x=2/9

2) -3(5⁰ - x)³ = 81

=> (1 - x)³ = 81 : (-3)

=> (1 - x)³ = -27

=> (1 - x)³ = (-3)³

=> 1 - x = -3

=> x = 1  + 3

=> x  = 4

2. suy ra (1-x )³ =81: (-3)=-27 =(-3)³

suy ra 1-x=-3 

     x=4

1. Bạn tính đi mình tính không được nó ra \(\pm\frac{\sqrt{55}}{\sqrt{3}}\)

Mà lớp 6 chưa học căn bậc hai mờ :>>>

\(2.-3(5^0-x)^3=81\)

\(\Rightarrow(5^0-x)^3=81\div(-3)\)

\(\Rightarrow(1-x)^3=-27\)

\(\Rightarrow(1-x)^3=(-3)^3\)

\(\Rightarrow1-x=-3\)

\(\Rightarrow x=1--3\)

\(\Rightarrow x=1+3\)

\(\Rightarrow x=4\)

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