Bài 6: Tính chất của phép cộng các số nguyên

a: =1048,8

b: =104,88

c: =10,488

d: =-104880

a) 2,3 . 456 =1048,8

b) 2,3 .45,6 =104,88

c) (-2,3) . (- 4,56) =10,488

d) (- 2,3) . 45 600 =-104880

a: =160

b: =0,5x0,7=0,35

c: =-0,8x0,006=-3/625

d: =0,2x(-0,2)=-0,04

a) \(\left(29,42+20,58\right)-\left(34,23+25,77\right)\)

\(=50-60=-10\)

b) \(-\left(212,49+87,51\right)+99,9\)

\(=-300+99,9=-200,1\)

A)29.42+20.58−34.23+(−25.77)29.42+20.58−34.23+(−25.77) 

=29.42+20.58−34.23−25.77

=29.42+20.58−34.23−25.77

=(29.42+20.58)−(34.23+25.77)

=(29.42+20.58)−(34.23+25.77)

=50−60=50−60

=−10=−10

B).(−212.49)−(87.51−99.9)(−212.49)−(87.51−99.9) 

=−212.49−87.51+99.9

=−212.49−87.51+99.9

=−(212.49+87.51)+99.9

=−(212.49+87.51)+99.9

=−300+99.9=−300+99.9

=−(300−99.9)=−(300−99.9)

=−200.1

 a) 637,07

b) 17,86

c) -56,63

d) 21,53

a) 324,82+312,25 = 637,07                     

b) (-12,07)+(-5,79)= 17,86

c) (-41,29)-15,34 = -56,63

d) (-22,65)-(-1,12)=  21,53

6.23

a)\(\dfrac{-5}{3}\) - \(\dfrac{-7}{3}\)

=\(\dfrac{-5-\left(-7\right)}{3}\)

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

b)\(\dfrac{5}{6}\)- \(\dfrac{8}{9}\) 

=\(\dfrac{5.3}{6.3}\)- \(\dfrac{8.2}{9.2}\)

=\(\dfrac{15}{18}\)-\(\dfrac{16}{18}\)

=\(\dfrac{-1}{18}\)

6.24 

A=(-\(\dfrac{3}{11}\)) + \(\dfrac{11}{8}\) - \(\dfrac{3}{8}\) + (-\(\dfrac{8}{11}\))

= [ (-\(\dfrac{3}{11}\)) +  (-\(\dfrac{8}{11}\)) ] + ( \(\dfrac{11}{8}\) - \(\dfrac{3}{8}\) )

=\(\dfrac{-11}{11}\) + \(\dfrac{8}{8}\)

= -1 + 1

=0

Tổng phần lương đã chi tiêu và mua quà là:
\(\dfrac{2}{5}\) + \(\dfrac{1}{4}\) = \(\dfrac{8}{20}\) + \(\dfrac{5}{20}\)=\(\dfrac{13}{20}\)

Phần tiền lương còn lại :

1 - \(\dfrac{13}{20}\) = \(\dfrac{20}{20}\) - \(\dfrac{13}{20}\) = \(\dfrac{7}{20}\)

đây 

\(3\left(2-x\right)+5\left(x-6\right)=-98\\ \Rightarrow6-3x+5x-30=-98\\ \Rightarrow2x-24=-98\\ \Rightarrow2x=-74\\ \Rightarrow x=-37\)

.
 

sai đầu bài bn ơi 6550 ko chia hết cho 19

\(\left(-7\right)+\left(-6\right)+\left(-5\right)+\left(-4\right)+\left(-3\right)+\left(-2\right)+\left(-1\right)\)
\(\Rightarrow\left(-28\right)\)

\(-8< x< 0\)

\(\Rightarrow x\in\left\{-7;-6;-5;-4;-3;-2;-1\right\}\)

Tổng các số nguyên \(x\) là:

\(\left(-7\right)+\left(-6\right)+\left(-5\right)+\left(-4\right)+\left(-3\right)+\left(-2\right)+\left(-1\right)=-28\)

\(27.3^{x-5}=3^{10}\\ \Rightarrow3^3.3^{x-5}=3^{10}\\ \Rightarrow3^{x-2}=3^{10}\\ \Rightarrow x-2=10\\ \Rightarrow x=12\)

12x=2020-16

12x=2004

x=2004:12=167

 12x + 16 = 2020 

12𝑥+16 = 2020−16

12x  = 2004 

x = 2004 : 12

x = 167

 12x + 16 = 2020 

12x = 2020 - 16

12x = 2004

x = 2004 : 12

x = 167