\(a,x-36:18=12-15\\ \Rightarrow x-2=-3\\ \Rightarrow x=-1\\ b,92-\left(17+x\right)=72\\ \Rightarrow17+x=20\\ \Rightarrow x=3\\ c,720:\left[41-\left(2x+5\right)\right]=40\\ \Rightarrow41-\left(2x+5\right)=18\\ \Rightarrow2x+5=23\\ \Rightarrow2x=18\\ \Rightarrow x=9\\ d,\left(x+2\right)^3-23=41\\ \Rightarrow\left(x+2\right)^3=64\\ \Rightarrow\left(x+2\right)^3=4^3\\ \Rightarrow x+2=4\\ \Rightarrow x=2\)

b: =>x+17=20

hay x=3

d: =>x+2=4

hay x=2

A = 1
B = 3
C = 9
D = 2

a) 90/x - 36/x-6 = 2.

ĐKXĐ: x≠0, x≠6.

<=> 90(x-6)-36x-2x(x-6)=0

<=> 90x-540-36x-2x²+12x=0

<=> -2x²+66x-540=0

<=> \(\left[{}\begin{matrix}x=18\left(tm\right)\\x=15\left(tm\right)\end{matrix}\right.\)

b) 1/x+1/x+10=1/12

ĐKXĐ: x≠0

<=> 1/x+1/x+10-1/12=0

<=> 12+12+10.12x-x=0

<=> 12+12+120x-x=0

<=> 119x+24=0

<=> 119x=-24

<=> x= -24/119(tm)

a) 58.57+58.150-58.125   

=58.(57+150-125)

=58.    82

=    4756        

b)3².5-2².7+83.2019⁰

=9.5-4.7+83

=45-28+83

=100

c)2019+(-247)+(-53)-2019 

 =(2019-2019)+[ (-247)+(-53)]

0+(-300)

= -300             

d)13.70-50 [(19-3²):2+2³]

=13.70-50[10:2+8]

=13.70-50.13

=13.(70-50)

=13.20

=260

2.

a)x-36:18=12-5   

    x-36:18=6

    x-36=6.18   

     x-36=108

      x=108+36

      x=    144                    

b)92-(17+x)=72

17+x=92-72

17+x=20

x=20-17

x=3

c)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=18

x=18:2

x=9                 

d) (x+2)³ -23=41

 (x+2)³ =41+23

 (x+2)³ =64

=> (x+2)³ =4³

=>x+2=4

=>x=4-2

=>x=2

a: \(\Leftrightarrow\dfrac{x}{-4}=\dfrac{21}{y}=\dfrac{z}{-80}=\dfrac{3}{4}\)

=>x=-3; y=28; z=-60

b: 5/12=x/-72

=>x=-72*5/12=-6*5=-30

c: =>x+3=-5

=>x=-8

9 + 18 + 27 + 36 + 45 + 54 + 63 + 72 + 90 = 414

kết quả là :

   414 

      đs...

1 x 9 = 9

2 x 9 = 18

3 x 9 = 27

4 x 9 = 36

5 x 9 = 45

6 x 9 = 54

7 x 9 = 63 

8 x 9 =72

9 x 9 = 81

10 x 9 = 90

Câu hỏi là : 9 + 18 + 27 + 36 + 45 + 54 + 63 + 72 + 81 +90 =414

a, \(\frac{5}{x+7}+\frac{8}{2x+14}=\frac{3}{2}\) Đkxđ : \(x\ne-7\)

⇔ \(\frac{5}{x+7}+\frac{8}{2\left(x+7\right)}=\frac{3}{2}\)

⇔ \(\frac{10}{2\left(x+7\right)}+\frac{8}{2\left(x+7\right)}=\frac{3\left(x+7\right)}{2\left(x+7\right)}\)

⇒ \(10+8=3\left(x+7\right)\)

⇔ \(10+8=3x+21\)

⇔ \(-3x=21-10-8\)

⇔ \(-3x=3\)

⇔ \(x=-1\) ( tm )

Ptr có tập nhiệm : S \(=\left\{-1\right\}\)

b, \(\frac{x+3}{x-3}-\frac{1}{x}=\frac{3}{x\left(x-3\right)}\) Đkxđ : \(x\ne3;x\ne0\)

⇔ \(\frac{x\left(x+3\right)}{x\left(x-3\right)}-\frac{1\left(x-3\right)}{x\left(x-3\right)}=\frac{3}{x\left(x-3\right)}\)

⇒ \(x\left(x-3\right)-1\left(x-3\right)=3\)

⇔ \(x^2-3x-x+3=3\)

⇔ \(x^2-4x=0\)

⇔ \(x\left(x-4\right)=0\)

⇔ \(\left\{{}\begin{matrix}x=0\\x-4=0\end{matrix}\right.\)

⇔\(\left\{{}\begin{matrix}x=0\left(ktm\right)\\x=4\left(tm\right)\end{matrix}\right.\)

Ptr có tập nhiệm : S \(=\left\{4\right\}\)

a) \(24\times y+76\times y=100\)
\(\Rightarrow\left(24+76\right)\times y=100\)
\(\Rightarrow100\times y=100\)
\(\Rightarrow y=100:100\)
\(\Rightarrow y=1\)
b) \(125\times y-100\times y=1000\)
\(\Rightarrow\left(125-100\right)\times y=1000\)
\(\Rightarrow25\times y=1000\)
\(\Rightarrow y=1000:25\)
\(\Rightarrow y=40\)

a)\(=>y=1000:\left(24+76\right)=1000:100=10\)

b(\(=>y=1000:\left(125-100\right)=1000:25=40\)

a)ĐKXĐ:x\(\ne\)0 x\(\ne\)6

=>90(x-6)-36x=2x(x-6)

<=>90x-540-36x=2x²-12x

<=>2x²-12x=54x-540

<=>2x²-66x+540=0

<=>x²-33x+270=0

<=>(x²-15x)-(18x-270)=0

<=>(x-15)(x-18)=0

<=>x=15(tm) hoặc x=18(tm)

b)ĐKXĐ:x\(\ne\)0 x\(\ne\)3

sai đề

c)ĐKXĐ:x\(\ne\)-2 x\(\ne\)2

=>3(x-2)-2(x+2)+8=0

<=>3x-6-2x-4+8=0

<=>x-2=0

<=>x=2(L)

Vậy PT vô nghiệm

d)ĐKXĐ: x\(\ne\)-7

=>10+8=\(\dfrac{3}{2}\)(câu này hình như đề cũng sai)