1: \(\dfrac{4}{23}+\dfrac{5}{21}+\dfrac{1}{2}-\dfrac{4}{23}+\dfrac{16}{21}\)

\(=1+\dfrac{1}{2}\)

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

2: \(\left(\dfrac{1}{3}+\dfrac{12}{67}+\dfrac{13}{41}\right)-\left(\dfrac{79}{67}-\dfrac{28}{41}\right)\)

\(=\dfrac{1}{3}+\dfrac{12}{67}+\dfrac{13}{41}-\dfrac{79}{67}+\dfrac{28}{41}\)

\(=\dfrac{1}{3}\)

Đáp án:

 a, 38+41+117+159+6238+41+117+159+62

=(38+62)+(41+159)+117=(38+62)+(41+159)+117

=100     +200      +117=100     +200      +117

=417=417

b, 73+86+968+914+303273+86+968+914+3032

=73+(86+914)+(968+3032)=73+(86+914)+(968+3032)

=73+1000     +4000=73+1000     +4000

=5073=5073

c, 341.67+341.16+659.83341.67+341.16+659.83

=341.(67+16)+659.83=341.(67+16)+659.83

=341.83+659.83=341.83+659.83

=83.(341+659)=83.(341+659)

=83.1000=83000=83.1000=83000

d, 42.53+47.156−47.11442.53+47.156-47.114

=42.53+47.(156−114)=42.53+47.(156-114)

=42.53 +47.42=42.53 +47.42

=42.(53+47)=42.100=42.(53+47)=42.100

=4200=4200

e, 563.23+23.26+23563.23+23.26+23

=23.(563+26+1)=23.(563+26+1)

=23.600=23.600

=13800=13800

f, 132+157+43+68132+157+43+68

=(132+68)+(157+43)=(132+68)+(157+43)

=200      +200=400=200      +200=400

g, 49.68+100.34+6849.68+100.34+68

=49.68+50.68+68=49.68+50.68+68

=68.(49+50+1)=68.(49+50+1)

=68.100=6800=68.100=6800

h, 491.(267+53)+491.(151+67)491.(267+53)+491.(151+67)

=491.(267+53+151+67)=491.(267+53+151+67)

=491.538=491.538

=264158=264158

Vote mk nha.

c: \(=0.5\cdot10-9=5-9=-4\)

c: 

một đơn vị vận tải đã huy động 8 xe để chở 480 tấn hàng trong thời gian quy định sau khi trở được 160 tấn thì đơn vị được giao nhiệm vụ chở 640 tấn nủa .Hỏi đơn vị phải huy động thêm bao nhiêu xe?

a: (-14)+(-16)+24

=-14-16+24

=-30+24

=-6

b: |-25|x71+29x25

\(=25\cdot71+25\cdot29\)

\(=25\left(71+29\right)=25\cdot100=2500\)

c: \(=132:\left(41+28-5^2\right)\)

\(=132:\left(69-25\right)=132:44=3\)

`a)1/[x-5x^2]-[25x-15]/[25x^2-1]`

`=[-(5x+1)-x(25x-15)]/[x(5x-1)(5x+1)]`

`=[-5x-1-25x^2+15x]/[x(5x-1)(5x+1)]`

`=[-25x^2+10x-1]/[x(5x-1)(5x+1)]`

`=[-(5x-1)^2]/[x(5x-1)(5x+1)]`

`=[1-5x]/[x(5x+1)]`

________________________________________________-

`b)(-1/[x^2-4x]+2/[16-x^2]-[-1]/[4x+16]):1/[4x]`

`=[-4(x+4)-8x+x(x-4)]/[4x(x-4)(x+4)].4x`

`=[-4x-16-8x+x^2-4x]/[(x-4)(x+4)]`

`=[x^2-16x-16]/[x^2-16]`

a,54.(41+59)-54.85

 = 54. 100 - 4590

= 5400- 4590

= 810

b,120.14+14.30

= 1680 +420

= 2100

Học tốt

\(a,54\cdot\left(41+59\right)-54\cdot85\)

\(=54\cdot100-54\cdot85\)

\(=54\cdot\left(100-85\right)\)

\(=54\cdot15=810\)

\(b,120\cdot14+14\cdot30\)

\(=14\cdot\left(120+30\right)\)

\(=14\cdot150=2100\)