a) 17,34 x 99 + 18 - 0,66

= 17,34 x 99 + 17,34 x 1

= 17,34 x (99 + 1)

= 17,34 x 100

= 1734

b) 7,63 x 12,47 + 12,47 x 2,37

= 12,47 x (7,63 + 2,37)

= 12,47 x 10

= 124,7

c) 112,37 x 4,29 - 4,29 x 12,37

= 4,29 x (112,37 - 12,37)

= 4,29 x 100

= 429

d) 17,4 x 52 + 57 x 17,4 - 17,4 x 9

= 17,4 x (52 + 57 - 9)

= 17,4 x 100

= 1740

A) 4,29 x 1230 - 429 x 2,3

= 429 x 12,3 - 429 x 2,3

= 429 x ( 12,3 - 2,3 )

= 429 x 10

= 4290

B) 30 - 15 + 36 - 18 + 42 - 21 + ... + 96 - 48 + 102 - 51

= ( 15 + 15 ) - 15 + ( 18 + 18 ) - 18 + ... + ( 48 + 48 ) - 48 + ( 51 + 51 ) - 51

= 15 + 18 + 21 + ... + 48 + 51

= [( 51 - 15 ) : 3 + 1] x ( 15 + 51 ) : 2

= [36 : 3 + 1] x 66 : 2

= [12 + 1] x 33

= 13 x 33

= 429

bạn nào giúp mình vs

\(a,1,5+2,5+...+8,5=\left(1,5+8,5\right)+\left(2,5+7,5\right)+\left(3,5+6,5\right)+\left(4,5+5,5\right)=10+10+10+10=40\\ b,7,63\times12,47+12,47\times2,37=12,47\times\left(7,63+2,37\right)=12,47\times10=124,7\)

\(c,37,2\times101-37-0,2=37,2\times101-\left(37+0,2\right)=37,2\times101-37,2=37,2\times\left(101-1\right)=37,2\times100=3720\)

\(d,112,37\times4,29-4,29\times12,37=4,29\times\left(112,37-12,37\right)=4,29\times100=429\)

a.

= ( 1,5 + 8,5 ) + ( 2,5 + 7,5 ) + ( 3,5 + 6,5 ) + ( 4,5 + 5,5 )

= 10 + 10 + 10 + 10 

= 40 

b.

= 12,47x(7,63+2,37)

= 12,47x10

=124,7

c.

= 37,2 x 101 - ( 37 + 0,2 )

= 37,2 x 101 - 37,2 x 1

= 37,2 x ( 101 - 1 )

= 37,2 x 100

= 3720

d.

=4,29x(112,37-37)

=4,29x100

=429

\(a,0,2x+7,51=-4,29\)

\(\Rightarrow0,2x=-4,29-7,51\)

\(\Rightarrow0,2x=-11,8\)

\(\Rightarrow x=-11,8:0,2=-59\)

\(b,\text{ }\frac{1}{3}\cdot x+\frac{2}{5}\cdot\left(x+1\right)=0\)

\(\frac{1}{3}\cdot x+\frac{2}{5}\cdot x+\frac{2}{5}=0\)

\(x\left(\frac{1}{3}+\frac{2}{5}\right)+\frac{2}{5}=0\)

\(x\cdot\frac{11}{15}+\frac{2}{5}=0\)

\(x\cdot\frac{11}{15}=0-\frac{2}{5}\)

\(x\cdot\frac{11}{15}=\frac{3}{5}\)

\(x=\frac{3}{5}\text{ : }\frac{11}{15}\)

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

\(b,\text{ }\frac{1}{3}\cdot x+\frac{2}{5}\cdot\left(x+1\right)=0\)

\(\frac{1}{3}\cdot x+\frac{2}{5}\cdot x+\frac{2}{5}=0\)

\(x\left(\frac{1}{3}+\frac{2}{5}\right)+\frac{2}{5}=0\)

\(x\cdot\frac{11}{15}+\frac{2}{5}=0\)

\(x\cdot\frac{11}{15}=0-\frac{2}{5}\)

\(x\cdot\frac{11}{15}=\frac{3}{5}\)

\(x=\frac{3}{5}\text{ : }\frac{11}{15}\)

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

a ) đề là x + 5 = 23 đúng ko

x = 18

b ) x = 32

c ) x = 12

d ) x = 7

e ) x = 34

f ) x = 17

g ) x = 135

h ) x = 1

Xin lỗi nha bài a) x + 5 = 23 mới đúng !

5.x-30=25

=> 5.x=25+30

=> 5.x=55

=> x=55:5

=> x=11

(x.17)+29=60

=> x.17=60-29

=> x.17=31

=> x=31:17

=> x=31/17

(49-x)+18=32

=> 49-x=32-18

=> 49-x=14

=> x=49-14

=> x=35

70-(x+19)=18

=> x+19=70-18

=> x+19=52

=> x=52-19

=> x=33

a) = (x+3).(x-3)^2-(x-3)(x+3)^2

=(x^2-9)(x-3)-(x^2-9)(x+3)

=(x^2-9)(x-3-x-3)

=-6(x^2-9)

các câu còn lại tương tự

\(a,\left(x+3\right)\left(x^2-3x+9\right)-\left(x-3\right)\left(x^2+3x+9\right)\)

\(=x^3+3-\left(x^3-3\right)\)

\(=x^3+3-x^3+3\)

\(=6\)

\(b,\left(x-5\right)\left(x^2+5x+25\right)-\left(x+5\right)\left(x^2-5x+25\right)\)

\(=x^3-5^3-x^3-5^3\)

\(=-125-125\)

\(=-250\)

a) X + 15 = 20

       X = 20 – 15

       X = 5

b) X – 18 = 16

       X = 16 + 18

       X = 34

c) 72 – x = 50

       X = 72 -50

       X =22

d) X x 7 = 42

       X= 42 : 7

       X = 6

e) X : 7 = 5

       X = 5 x 7

       X = 35

f) 49 : x = 7

       X = 49: 7

       X = 7