\(\frac{254^5+254^6}{254^3.254^2}=\frac{254^3.254^2+254^6}{254^3.254^2}=254^6\)

\(\frac{254^5+254^6}{254^3\cdot254^2}=\frac{254^5\left(1+254\right)}{254^5}=1+254=255\)

254⁵⁺⁶:254³⁺²

=254¹¹:254⁵

=254⁶

255
 

1-2+3-4+5-6+...+253-254

=(-1)+(-1)+(-1)+...+(-1)

=(-1)x127

=(-127)

Ai giúp mk với 

1: (-49)+153+(-31)

=153-(49+31)

=153-80

=73

2: (-215)+115+(-83)

=(-215+115)+(-83)

=-100-83

=-183

3: 154+(-68)+(-254)+368

=(154-254)+(-68+368)

=-100+300

=200

4: 146+(-37)+254+(-163)

=(146+254)-(37+163)

=400-200

=200

5: -(-357)+27+(-357)+(-32)

=(357-357)+(27-32)

=0+(-5)=-5

6: (-25)+15+(-17)-(-25)+(-13)

=(-25+25)+15+(-17-13)

=15-30

=-15

A)\(\frac{254\cdot399-145}{254+399\cdot253}\)

\(=\frac{\left(253+1\right)\cdot399-145}{254+399\cdot253}\)

\(=\frac{253\cdot399+1\cdot399-145}{254+399\cdot253}\)

\(=\frac{253\cdot399+399-145}{254+399\cdot253}\)

\(=\frac{253\cdot399+254}{254+399\cdot253}\Rightarrow=1\)

B) X x X - 1/6 = 5/18

x² = 5/18 + 1/6

x² = 8/18 = 4/9

x= \(\sqrt{\frac{4}{9}}\) \(=\frac{2}{3}\)

2.(x+5)+126=x+1000-254

2.x+10+126=x+746

x+x+136=x+746

=>x+136=746

x=746-136

x=610

chúc bạn học tốt nha

2 . ( x + 5 ) + 126 = x + 1000 - 254 

<=> 2 . x +  2 . 5 + 126 = x + 746 

<=> 2 . x + 10 + 126 = x + 746

<=> 2 . x + 136 = x + 746 

<=> 2 . x - x = 746 - 136 

<=> 2 . x - x . 1 = 610

<=> x . ( 2 - 1 ) = 610 

<=> x . 1 = 610 

<=> x = 610 : 1 

<=> x = 610 

Vậy x = 610 

   254 - 49 - 75 + 254 - 175 + 549

= ( 549 - 49 ) - ( 175 + 75 ) + 254 + 254

= 500 - 250 + 254 + 254

= 758