[ ( 9 - 18 ) + ( -17 ) ] + ( -15 )

= [ ( -9 ) + ( -17 ) ] + ( -15 )

= ( -26 ) + ( -15 )

= -41

666 - ( -442 ) - 100 - 88

= 666 + 442 - 100 - 88

= 1108 - 100 - 88

= 1008 - 88

= 920

- ( -315 ) + ( -115 ) - 105 + 25

= 315 + ( -115 ) - 105 + 25

= 200 - 105 + 25

= 95 + 25

= 120

888 - ( -333 ) - 222 + 70

= 888 + 333 - 222 + 70

= 1221 - 222 + 70

= 999 + 70

= 1069

a, 32+68:17×5-29

=32+4×5-29

=32+20-29

=52-29

=23

b, 15×48-30×24+115

=720-720+115

=0+115

=115

a) 32 + 68 : 17 x 5 - 29 = 23

b) 15 x 48 - 30 x 24 + 115 = 15 x 48 - 15 x 2 x 24 + 115

                                          =  15 x 48 - 15 x 48 + 115

                                          = 0 + 115

                                          = 115

goodluck!!

a, 32 + 68 : 17 x 5 - 29 

= 32 + 4 x 5 - 29

= 32 + 20 - 29

= 52 - 29

= 23

b, 15 x 48 - 30 x 24 + 115

= 720 - 720 + 115

= 0 + 115

= 115

Hok tốt !

(115-15):2+1=51(số);51.(115+15):2=3315

tick mk nha
 

Có số số hạng là :

( 115 - 15 ) : 2 + 1 = 51 ( số )

Tổng đó là :

( 115 + 15 ) x 51 : 2 = 3315

1, 17.(-84) + 17.(-16)

= - 17.84 - 17.16

= -17.(84 + 16)

= -17.100

= -1700

2; 15.(58) - 15.(48)

= 15.(58 - 48)

= 15. 10

= 150

3, -37.86 + 37.76

= -37.(86 - 76)

= -37.10

= - 370

4, 1975.(-115) + 1975.75

= 1975. (-115  + 75)

= 1975 .(-40)

= - 79000 

5, 79.89 - 79.(-11)

= 79.(89 + 11)

= 79.100

= 7900

1, 17.(-84) + 17.(-16)

= - 17.84 - 17.16

= -17.(84 + 16)

= -17.100

= -1700

2; 15.(58) - 15.(48)

= 15.(58 - 48)

= 15. 10

= 150

3, -37.86 + 37.76

= -37.(86 - 76)

= -37.10

= - 370

4, 1975.(-115) + 1975.75

= 1975. (-115  + 75)

= 1975 .(-40)

= - 79000 

5, 79.89 - 79.(-11)

= 79.(89 + 11)

= 79.100

= 7900

a,(x+1)(x-20)=0

  =>x+1=0 va x-20=0

=>x=-1 va x=20

a, X=-1;x=20.

b,x=-147

c,x=-110

y \(\times\) \(\dfrac{16}{64}\) + y \(\times\) \(\dfrac{25}{100}\) + y \(\times\) \(\dfrac{1}{4}\) + y \(\times\) \(\dfrac{15}{60}\) -  \(\dfrac{13}{15}\) = \(\dfrac{17}{15}\)

y \(\times\) ( \(\dfrac{1}{4}\) + \(\dfrac{1}{4}\) + \(\dfrac{1}{4}\)+ \(\dfrac{1}{4}\)) - \(\dfrac{13}{15}\) = \(\dfrac{17}{15}\)

y                             = \(\dfrac{17}{15}\) + \(\dfrac{13}{15}\)

y = \(\dfrac{30}{15}\)

y = 2

Cái này bằng rủ em chơi oẳn tù tì ,em ra lá còn anh ra hôn má em

me nhìn công thức của cô Hoài moà đâu đầu nun á

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

\(\left\{{}\begin{matrix}x+y=1000\\\dfrac{15}{100}x+\dfrac{17}{100}y=1162\end{matrix}\right.\)

=>\(\left\{{}\begin{matrix}\dfrac{15}{100}x+\dfrac{15}{100}y=150\\\dfrac{15}{100}x+\dfrac{17}{100}y=1162\end{matrix}\right.\)

=>\(\left\{{}\begin{matrix}-\dfrac{2}{100}y=150-1162=-1012\\x+y=1000\end{matrix}\right.\)

=>\(\left\{{}\begin{matrix}y=50600\\x=1000-50600=-49600\end{matrix}\right.\)