a)12.(x-5)+7(3-x)=5

\(\Rightarrow12x-60+21-7x-5=0\)

\(\Rightarrow5x-44\)

\(\Rightarrow x=\frac{44}{5}\)

Vậy: \(x=\frac{44}{5}\)

b)\(2x^2-3=29\)

\(\Rightarrow2x^2=3+29=32\)

\(\Rightarrow x^2=\frac{32}{2}=16\)

\(\Rightarrow x=\sqrt{16}=4\)

Vậy: \(x=4\)

Chúc bạn học tốt!!!

a) 12.(x-5)+7(3-x)=5

12x -60+21-7x =5

5x - 39 =5

5x = 44

x = 44/5

b)2.x²-3 =29

2x² = 32

x² = 16

x² = 4²

x =4

khó quá ??????????????????????????????????

a) (-2) . ( x+7 ) + (-5) = 7 

<=>(-2).(x+7)=7+5

<=>x+7=12:(-2)

<=>x+7=-6

<=>x=(-6)-7

<=>x=-13

Vậy x=-13

b)(x+4) : (-7) = 14

<=>x+4=14 x (-7)

<=>x+4=-98

<=>x=-98-4

<=>x=-102

Vậy x= -102

c) 72 : ( x+5) - 4 = -12 

<=>72:(x+5)=(-12)+4

<=>x+5=72:(-8)

<=>x+5=-9

<=>x=-9-5

<=>x=-14

Vậy x= -14

d) (x+3) : (-6 ) + 12 = 8 

<=>(x+3) :(-6)=8-12

<=>x+3=(-4)x(-6)

<=>x+3=24

<=>x=24-3

<=>x=21

Vậy x= 21 

\(4,7\div0,25+5,3\times4\)

\(=18,8+21,2\)

\(=40\)

\(3\times\left(a-2\right)+150=240\)

\(3\times\left(a-2\right)=90\)

\(a-2=30\)

\(a=32\)

\(\dfrac{1}{9}+a+\dfrac{7}{12}=\dfrac{17}{18}\)

\(\dfrac{1}{9}+a=\dfrac{13}{36}\)

\(a=\dfrac{1}{4}\)

\(\left(\dfrac{1}{2}\times\dfrac{1}{3}+\dfrac{1}{3}\times\dfrac{1}{4}+\dfrac{1}{4}\times\dfrac{1}{5}+\dfrac{1}{5}\times\dfrac{1}{6}+\dfrac{1}{6}\times\dfrac{1}{7}+\dfrac{1}{7}\times\dfrac{1}{8}\right)\times a=\dfrac{9}{16}\)

\(\left(\dfrac{1}{2\times3}+\dfrac{1}{3\times4}+\dfrac{1}{4\times5}+\dfrac{1}{5\times6}+\dfrac{1}{6\times7}+\dfrac{1}{7\times8}\right)\times a=\dfrac{9}{16}\)

\(\left(\dfrac{1}{2}-\dfrac{1}{8}\right)\times a=\dfrac{9}{16}\)

\(\dfrac{3}{8}\times a=\dfrac{9}{16}\)

\(a=\dfrac{3}{2}\)

`-5/8xx5/12+5/8xx(-7/12)+17/8`

`=5/8xx(-5/12)+5/8xx(-7/12)+17/8`

`=5/8xx(-5/12-7/12)+17/8`

`=5/8xx(-12)/12+17/8`

`=5/8xx(-1)+17/8`

`=-5/8+17/8`

`=12/8=3/2`

\(-\dfrac{5}{8}\cdot\dfrac{5}{12}+\dfrac{5}{8}\cdot\left(-\dfrac{7}{12}\right)+\dfrac{17}{8}\)
\(=-\dfrac{5}{8}\cdot\dfrac{5}{12}+-\dfrac{5}{8}\cdot\dfrac{7}{12}+\dfrac{17}{8}\)
\(=-\dfrac{5}{8}\left(\dfrac{5}{12}+\dfrac{7}{12}\right)+\dfrac{17}{8}\)
\(=-\dfrac{5}{8}\cdot1+\dfrac{17}{8}\)
\(=-\dfrac{5}{8}+\dfrac{17}{8}\)
\(=\dfrac{12}{8}=\dfrac{3}{2}\)

Cảm ơn hai bn(⌒▽⌒)🥰🥰🥰

a) 3+x=-8

x=-8+3

x=-5

b: =>25-x=29

hay x=-4

a) 3 + x = -8                b) (25 - x) - 12 = 27                       c) 2^x + 15 = 31

          x = -8 - 3                25 - x          = 27 + 12                   2^x         = 31 - 15 

          x = -11                   25 - x          = 39                            2^x         = 16

Vậy x = -11                             x          = 25 - 39                     2^x         = 2⁴

                                               x           = - 14                      => x = 4

                                          Vậy x = -14                               Vậy x = 4

Vì 1/x(x+1) = 1/x - 1/(x+1) nên 
vế trái = 2(1/2.3 + 1/3.4 + ... + 1/x(x+1)) 
=2( 1/2 - 1/3 + 1/3 - 1/4 +...+ 1/x - 1/(x+1) 
=2( 1/2 - 1/(x+1) 
= x/(x+1) 
Đến đây thì bạn tự thay vào rồi giải tiếp

nha

a) (-5²+1)-9.3

=26-27

=-1

b)80-(4.5²-3.2³)

=80-(100-24)

=80-76

=4

c) [(-18)+(-7)]-15

=-25-15

=-40

d) (-219)-(-229)+12.5

=10+60

=70

Đáp án của mình là:

3 ( |1 - x | - 2 ) + 1 = 7

3 ( |1 - x | - 2 ) = 7 - 1

3 ( |1 - x | - 2 ) = 6

1 - x - 2 = 6 : 3

1 - x - 2 = 2

1 - x  = 2 + 2

1 - x  = 4

x = 1 - 4

x = -3

nhé bạn!

__HT__