A,1,Số số hạng trong dãy số trên là

(26-17):1+1=10 (số)

Tổng dãy số trên là

(26+17)x10/2=215

2,48x(17+1)=48x18=864

3,28x51+14x86+14x2

14x2x51+14x86+14x2

14x102+14x86+14x2

14x190=2660

4,341(67+16)+659x83

341x83+659x83=(341+659)x83=1000x83=83000

(34044-324x67):48-48

= (34044-21708):48-48

= 12336:48-48

= 257 -48

= 209

=>x-1=0

hay x=1

đề bài cho như này 9^x-1 = 1 hay như này vậy 9^x - 1 = 1

a)67.153-53.67+712:8

=67.(153-53)+89

=67.100+89

=6789

\(a,67\times153-53\times67+712:8\)

\(=67\times\left(153-53\right)+\left(712:8\right)\)

\(=67\times100+89\)

\(=6700+89\)

\(=6789\)

\(b,168-\left\{5\times\left[143-\left(15-12\right)^2\right]+10\right\}:10\)

\(=168-\left\{5\times\left[143-3^2\right]+10\right\}:10\)

\(=168-\left\{5\times134+10\right\}:10\)

\(=168-\left\{670+10\right\}:10\)

\(=168-680:10\)

\(=168-68\)

\(=100\)

\(c,\left(-13\right)+84+\left(-87\right)+16\)

\(=13+84-87+16\)

\(=\left(13+87\right)-\left(84+16\right)\)

\(=100-100\)

\(=0\)

\(d,9-\left(12-15\right)\)

\(=9-\left(-3\right)\)

\(=12\)

\(\dfrac{11}{8}:x-\dfrac{2}{5}+-\dfrac{1}{6}=-\dfrac{1}{5}\\ =>\dfrac{11}{8}:x-\dfrac{2}{5}=-\dfrac{1}{5}-\left(-\dfrac{1}{6}\right)\\ =>\dfrac{11}{8}:x-\dfrac{2}{5}=-\dfrac{1}{5}+\dfrac{1}{6}\\ =>\dfrac{11}{8}:x-\dfrac{2}{5}=-\dfrac{6}{30}+\dfrac{5}{30}\\ =>\dfrac{11}{8}:x-\dfrac{2}{5}=-\dfrac{1}{30}\\ =>\dfrac{11}{8}:x=-\dfrac{1}{30}+\dfrac{2}{5}\\ =>\dfrac{11}{8}:x=-\dfrac{1}{30}+\dfrac{12}{30}\\ =>\dfrac{11}{8}:x=\dfrac{11}{30}\\ =>x=\dfrac{11}{8}:\dfrac{11}{30}\\ =>x=\dfrac{11}{8}.\dfrac{30}{11}\\ =>x=\dfrac{30}{8}\\ =>x=\dfrac{15}{4}\\ \dfrac{4}{7}x-\dfrac{1}{3}x+\left(-\dfrac{16}{21}\right)=-\dfrac{2}{3}\\ =>\left(\dfrac{4}{7}-\dfrac{1}{3}\right)x=-\dfrac{2}{3}-\left(-\dfrac{16}{21}\right)\\ =>\left(\dfrac{12}{21}-\dfrac{7}{21}\right)x=-\dfrac{2}{3}+\dfrac{16}{21}\\ =>\dfrac{5}{21}x=-\dfrac{14}{21}+\dfrac{16}{21}\\ =>\dfrac{5}{21}x=\dfrac{2}{21}\\ =>x=\dfrac{2}{21}:\dfrac{5}{21}\)

\(=>x=\dfrac{2}{21}.\dfrac{21}{5}\\ =>x=\dfrac{2}{5}\\ -\dfrac{11}{12}x+\dfrac{15}{2}\left(x+-\dfrac{1}{5}\right)=\dfrac{67}{8}\\ =>-\dfrac{11}{12}x+\dfrac{15}{2}.x-\dfrac{1}{5}=\dfrac{67}{8}\\ =>\left(-\dfrac{11}{12}+\dfrac{15}{2}\right)x=\dfrac{67}{8}+\dfrac{1}{5}\\ =>\left(-\dfrac{11}{12}+\dfrac{90}{12}\right)x=\dfrac{335}{40}+\dfrac{8}{40}\\ =>\dfrac{79}{12}x=\dfrac{343}{40}\\ =>x=\dfrac{343}{40}:\dfrac{79}{12}\\ =>x=\dfrac{343}{40}.\dfrac{12}{79}\\ =>x=\dfrac{343.12}{40.79}\\ =>x=\dfrac{343.3}{10.79}\\ =>x=\dfrac{1029}{790}\)

b. 16×25+44×100/ 29×96+142×48

=400+4×11×100/29×96+71×2×48

=400+400×11/29×96+71×96

=400×(1+11)/96×(29+71)

=400×12/96×100=1/2

\(\frac{8.15.42}{16.21.45}=\frac{8.15.21.2}{8.2.21.15.3}=\frac{1}{3}\)

\(\frac{25.33.60.7}{21.65.121.48}=\frac{5.5.11.2.12.5.7}{7.3.13.5.11.12.12.4}=\frac{25}{572}\)

Đề : Em muốn tham gia học ngoại khóa môn bơi lội  ở nhà văn hóa thiếu nhi tiinhr đồng nai. Em hãy viết lá đơn xin tham gia khóa học đó

làm hộ mình nhé 

\(\frac{8\cdot15\cdot42}{16\cdot21\cdot45}=\frac{8\cdot15\cdot21\cdot2}{2\cdot8\cdot21\cdot15\cdot3}=\frac{1}{3}\)

\(\frac{25\cdot33\cdot60\cdot7}{21\cdot65\cdot121\cdot48}=\frac{5\cdot5\cdot3\cdot11\cdot12\cdot5\cdot7}{3\cdot7\cdot13\cdot5\cdot11\cdot11\cdot12\cdot4}=\frac{5\cdot5}{13\cdot11\cdot4}=\frac{25}{572}\)

a) 460 + 85.4 = ( x + 200 ) : 4

=> x = 3000

b) => x = 2595

c) => x = 50

d) => x = 40

a)460 +85 . 4 = (x+200) :4                                                      b)x:15+42=15+25.8

 suy ra :  460+340=(x+200):4                                                  suy ra: x:15+42=15+200

suy ra:   800= (x+200):4                                                           suy ra : x:15+42=215

 suy ra : 800.4=x+200                                                             suy ra: x:15=215-42

 suy ra : 3200=x+200                                                               suy ra : x:15=173

suy ra: x= 3200-200                                                                 suy ra : x=173.15

suy ra : x=3000          vậy x =3000                                            suy ra: x=2595                 vậy x = 2595

  c) x-32:16=48                                                                d)x-6:2-(48-24.2:6-3)=0

suy ra :x-2=48                                                                   suy ra : x-6:2-(48-48:6-3)=0

suy ra :x=48+2                                                                    suy ra : x-6:2-(48-8-3)=0

suy ra : x=50                                                                     suy ra : x-6:2-(40-3)=0

 vậy x=50                                                                         suy ra : x-6:2 - 37=0

                                                                                        suy ra : x-3-37=0

                                                                                      suy ra : x-3=0+37

                                                                                    suy ra : x-3=37

                                                                                     suy ra : x=37+3

                                                                                        suy ra :x=40             vậy x= 40