a, \(\dfrac{10}{17}\) + \(\dfrac{5}{-13}\) - \(\dfrac{11}{25}\) + \(\dfrac{7}{17}\) - \(\dfrac{8}{13}\)

= ( \(\dfrac{10}{17}\) + \(\dfrac{7}{17}\)) - ( \(\dfrac{5}{13}\) + \(\dfrac{8}{13}\)) - \(\dfrac{11}{25}\)

= \(\dfrac{17}{17}\) - \(\dfrac{13}{13}\) - \(\dfrac{11}{25}\)

= 1 - 1 - \(\dfrac{11}{25}\)

= - \(\dfrac{11}{25}\)

b, 0,3 - \(\dfrac{93}{7}\) - 70% - \(\dfrac{4}{7}\)

= 0,3 - 0,7 - ( \(\dfrac{93}{7}+\dfrac{4}{7}\))

= - 0,4 - \(\dfrac{97}{7}\)
= - \(\dfrac{2}{5}\) - \(\dfrac{97}{7}\)

= - \(\dfrac{499}{35}\)

c, \(\dfrac{1}{8}\) + \(\dfrac{1}{24}\) + \(\dfrac{1}{48}\)+ ...+ \(\dfrac{1}{2400}\)

= \(\dfrac{1}{2\times4}\)  +\(\dfrac{1}{4\times6}\) + \(\dfrac{1}{6\times8}\) +...+ \(\dfrac{1}{48\times50}\)

= \(\dfrac{1}{2}\) \(\times\) ( \(\dfrac{2}{2\times4}\) +\(\dfrac{2}{4\times6}\)+ \(\dfrac{2}{6\times8}\) +...+ \(\dfrac{2}{48\times50}\))

= \(\dfrac{1}{2}\) \(\times\) ( \(\dfrac{1}{2}\) - \(\dfrac{1}{4}\) + \(\dfrac{1}{4}\) - \(\dfrac{1}{6}\) + \(\dfrac{1}{6}\) - \(\dfrac{1}{8}\) +...+ \(\dfrac{1}{48}\) - \(\dfrac{1}{50}\))

= \(\dfrac{1}{2}\) \(\times\) ( \(\dfrac{1}{2}\) - \(\dfrac{1}{50}\))

= \(\dfrac{1}{2}\) \(\times\) \(\dfrac{12}{25}\)

= \(\dfrac{6}{25}\)

Lời giải chi tiết:

A , 6x - 5 = 613

     6x      = 618

       x      = 103

b , x - 48 : 16 = 25

     x - 3          = 25

     x               = 28

c , ( x - 8 ) . ( x - 7 ) = 0

=> x - 8 = 0 hoặc x - 7 = 0

         x  = 8              x  = 7

Vậy x = 8 hoặc x = 7

a, x=103

b, x=28

c, x=0

1 ) ( 75 - 200 ) - ( - 100 - 25 )

= 75 - 200 + 100 + 25

= ( 75 + 100 ) + ( - 200 + 25 )

= 175 + ( - 175 )

= 0

2) \(48+5\left(x-3\right)=63\)

\(5x-15=63-48\)

\(5x=15+15\)

\(5x=30\)

\(x=6\)

3) \(\left|x\right|-2=7-\left(-8\right)\)

\(\left|x\right|=7+8+2\)

\(\left|x\right|=17\)

\(\Rightarrow\orbr{\begin{cases}x=17\\x=-17\end{cases}}\)

4) \(\left|x+5\right|-3=-2\)

\(\left|x+5\right|=1\)

\(\Rightarrow\orbr{\begin{cases}x+5=1\\x+5=-1\end{cases}}\Rightarrow\orbr{\begin{cases}x=-4\\x=-6\end{cases}}\)

5)  \(\left(x-2\right)\left(x+5\right)=0\)

\(\Rightarrow\orbr{\begin{cases}x-2=0\\x+5=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=2\\x=-5\end{cases}}\)

80 - 4 . 5² + 3 .2³=80 - 4 . 25 + 3 . 8=80 - 100 +24=-20+24=4

25 . 124 - 24 . 25 +212=24 .(124 - 25)+212=24 . 99 +212=2376 +212=2588

35 . 48 + 65 . 68 + 20 . 35=35 . (48 +20)+65 . 68=35 . 68 +65 . 68=68 . (35 + 65)=68 . 100=6800

2⁷ :2³+2³.2⁰-1¹⁰=2⁴+2³- 1=16 + 8 -1=23

câu 3,câu 6,câu 7 mk ko làm đc vì ko biết cách viết dấu móc vuông với dấu móc kép nha bạn.:) ^_^

HOK TỐT

1) ( x - 2 ) . ( x + 15 ) = 0

\(\Rightarrow\) x - 2 = 0 hoặc x + 15 = 0

* Nếu x - 2 = 0

x = 0 + 2

x = 2

* Nếu x + 15 = 0

x = 0 - 15

x = -15

Vậy x \(\in\) { 2 ; -15 }

2) ( 7 - x ) . ( x + 19 ) = 0

\(\Rightarrow\) 7 - x = 0 hoặc x + 19 = 0

* Nếu 7 - x = 0

x = 7 - 0

x = 7

* Nếu x + 19 = 0

x = 0 - 19

x = -19

Vậy x \(\in\) {7 ; -19}

dễ mà

a) \(=300\)

b) \(=374\)

c) \(=4747\)

d) \(=180000\)

a)300

b)374

e)7000

`A=\sqrt{25/[3-2\sqrt{2}]}`

`A=\sqrt{[25(3+2\sqrt{2})]/[9-8]}`

`A=5\sqrt{3+2\sqrt{2}}`

___________

`B=\sqrt{[a^4 b^3]/[a^2 b-ab]}`       `(a > 1;b > 0)`

`B=\sqrt{[ab.a^3 b^2]/[ab(a-1)]}`

`B=ab\sqrt{a/[a-1]}`