\(426-\left\{3.\left[152-\left(5-2\right)^2\right]\right\}:10\\ =426-\left\{3.\left[152-3^2\right]\right\}:10\\ =426-\left\{3.\left[152-9\right]\right\}\\ =426-\left\{3.143\right\}\\ =426-429=-3\)

??? lớp 6 học cái bài toán như này á

426-{3.[152-(5-2)^2] +1} : 10=383

1672+[49+(13-7)^3]=1937

a) (426 + x) : 5 = 120

(=) 426 + x = 120 :5

(=) 426 + x = 24

(=) x = 24 - 426

(=) x = - 402

Vậy x = - 402

b) 5844 : x -159 = 328

(=) 5844 : x = 328+ 159

(=) 5844 : x = 487

(=) x = 5844 : 487

(=) x = 12

Vậy x = 12

 c) 3^2x + 1 = 27 

(=) 3^2x = 27 -1 

(=) 3^2x = 26 

=> vô lý 

vậy x thuộc tập hợp rỗng

d) (3x - 1)² = 64

(=) (3x - 1)² = 8²

(=) 3x - 1 = 8

(=) 3x = 8 + 1

(=) 3x = 9

(=) x = 9 : 3

(=) x = 3

Vậy x = 3

( 426 + x ) : 5 = 120

( 426 + x ) = 600

           x   = 600 - 426

           x  = 174

b ) 5844 : x - 159 = 328

     5844 : x         = 328 + 159

     5844 : x         = 487

               x         = 5844 : 487

               x          = 12

d ) ( 3x - 1 ) ² = 64

     ( 3x - 1 ) = 8

       3x        = 9

         x       = 3

\(\left(426+x\right):5=120\)

\(\Rightarrow\left(460+x\right)=600\)

\(\Rightarrow x=600-426\)

\(\Rightarrow x=174\)

c.\(\dfrac{3}{7}+\dfrac{5}{7}:x=\dfrac{1}{3}\)

\(\dfrac{5}{7}:x=\dfrac{1}{3}-\dfrac{3}{7}\)

\(\dfrac{5}{7}:x=-\dfrac{2}{21}\)

\(x=\dfrac{5}{7}:-\dfrac{2}{21}\)

\(x=-\dfrac{15}{2}\)

d.\(3\dfrac{1}{4}:\left|2x-\dfrac{5}{12}\right|=\dfrac{39}{16}\)

\(\left|2x-\dfrac{5}{12}\right|=3\dfrac{1}{4}:\dfrac{39}{16}\)

\(\left|2x-\dfrac{5}{12}\right|=\dfrac{4}{3}\)

\(\rightarrow\left[{}\begin{matrix}2x-\dfrac{5}{12}=\dfrac{4}{3}\\2x-\dfrac{4}{12}=-\dfrac{4}{3}\end{matrix}\right.\) \(\rightarrow\left[{}\begin{matrix}2x=\dfrac{7}{4}\\2x=-\dfrac{11}{12}\end{matrix}\right.\) \(\rightarrow\left[{}\begin{matrix}x=\dfrac{7}{8}\\x=-\dfrac{11}{24}\end{matrix}\right.\)

A, \(\dfrac{4}{9}+x=\dfrac{5}{3}\)

\(x\)\(=\dfrac{5}{3}-\dfrac{4}{9}\)

\(x\)\(=\dfrac{11}{9}\)

B,\(\dfrac{3}{4}.x=\dfrac{-1}{2}\)

\(x=\dfrac{-1}{2}:\dfrac{3}{4}\)

\(x=\)\(\dfrac{-2}{3}\)

a)

\(\frac{4}{9} + x = \frac{5}{3}\)

=> \(x = \frac{5}{3}-\frac{4}{9}\)

=> \(x = \) \(\frac{11}{9}\)

Vậy \(x = \dfrac{11}{9}\)

b) 

\(\dfrac{3}{4} .x = \dfrac{-1}{2}\)

=> \(x = \dfrac{-1}{2} : \dfrac{3}{4}\)

=> \(x = \dfrac{-2}{3}\)

Vậy \(x = \dfrac{-2}{3}\)

c)

\( \dfrac{3}{7}+ \dfrac{5}{7}:x = \dfrac{1}{3}\)

=> \(\dfrac{5}{7}:x = \dfrac{1}{3}-\) \( \dfrac{3}{7}\)

=> \(\dfrac{5}{7}:x = \dfrac{-2}{21}\)

=> \(x = \dfrac{5}{7}:\dfrac{-2}{21}\)

=> \(x = \dfrac{-15}{2}\)

Vậy \(x = \dfrac{-15}{2}\)

d) 

\(3\dfrac{1}{4} : |2x - \dfrac{5}{12} | = \dfrac{39}{16}\)

=> \(\dfrac{13}{4} : |2x - \dfrac{5}{12} | = \dfrac{39}{16}\)

=> \( |2x - \dfrac{5}{12} | =\dfrac{13}{4} : \dfrac{39}{16}\)

=> \(|2x-\dfrac{5}{12} |= \dfrac{4}{3}\)

=> \(\left[\begin{matrix} 2x - \dfrac{5}{12} = \dfrac{4}{3}\\ 2x - \dfrac{5}{12} = \dfrac{4}{3}\end{matrix}\right.\)

=> \(\left[\begin{matrix} 2x = \dfrac{-4}{3}+\dfrac{5}{12}\\ 2x = \dfrac{-4}{3}+\dfrac{5}{12} \end{matrix}\right.\)

=> \(\left[\begin{matrix} 2x = \dfrac{7}{4}\\ 2x = \dfrac{-11}{12} \end{matrix}\right.\)

=> \(\left[\begin{matrix} x = \dfrac{7}{8}\\ x = \dfrac{-11}{24} \end{matrix}\right.\)

Vậy \(x \in \) { \(\dfrac{7}{8} ; \dfrac{-11}{24}\) }

300

300

\((-87)+126+187+74 = 126 - 87 +187 + 74 = 39 + 187 +74=300\)

Tổng A có số số hạng là: (2019-1):2+1= 1010 số

Tổng A là: 1010.(2019+1):2=1020100

:))

số số hạng dãy trên là 

\(\left(2019-1\right):2+1=1010\)

tổng dãy trên là 

\(\left(2019+1\right).1010:2=1020100\)

vậy \(A=1+3+5+7+9+...+2017+2019=1020100\)

Số số hạng của A là :

( 2019 - 1 ) : 2 + 1 = 1010 ( số hạng )

Tổng của A là :

( 2019 + 1 ) \(\times\) 1010 : 2 = 1020100 

Đáp số : 1020100 .

Học tốt  ! 

\(a,\frac{4}{5}+\frac{17}{25}\)

\(=\frac{20}{25}+\frac{17}{25}\)

\(=\frac{37}{25}\)

\(b,\frac{7}{3}-\frac{5}{6}\)

\(=\frac{14}{6}-\frac{5}{6}\)

\(=\frac{9}{6}\)

\(=\frac{3}{2}\)

\(c,1+\frac{2}{3}\)

\(=\frac{3}{3}+\frac{2}{3}\)

\(=\frac{5}{3}\)

a)  4/5 + 17/25

=  20/25 + 17/25

=      37/25

b)  7/3 - 5/6

= 14/6 - 5/6

=     9/6

=     3/2

c)  1 + 2/3

= 3/3 + 2/3

=   5/3

a)4/5+17/25

=20/25+17/25

=37/25

b)7/3-5/6

=14/6-5/6

=9/6=3/2

c)1+2/3

=1/1+2/3

=3/3+2/3

=5/3

k nhé chúc bạn học giỏi

dễ thế mà cũng ko bik chia phan so = nhan đảo ngược

A. \(\frac{2}{5}\div\frac{2}{3}=\frac{2}{5}\times\frac{3}{2}=\frac{2\times3}{5\times2}=\frac{3}{5}\text{ }\)

B. \(\frac{4}{7}\div\frac{4}{5}=\frac{4}{7}\times\frac{5}{4}=\frac{4\times5}{7\times4}=\frac{5}{7}\)

C. \(\frac{1}{6}\div\frac{1}{3}=\frac{1}{6}\times\frac{3}{1}=\frac{3}{6}=\frac{1}{2}\)

D. \(\frac{1}{4}\div\frac{1}{8}=\frac{1}{4}\times\frac{8}{1}=\frac{8}{4}=2\)

= (3³) ³ và (3⁴) ⁵

=3⁹ và 3²⁰

Mà 3 ⁹ <3²⁰

Vậy 27⁷< 81⁵