a) (-234) + |-145| + (-2019) + |155| + (-66)

= -234 + 145 - 2019 + 155 - 66

= (-234 - 66) + (145 + 155) - 2019

= -300 + 300 - 2019

= 0 - 2019 = -2019

b) -79.|-45| - 21.|45|

= -79.45 - 21.45

= (-79 - 21) . 45

= -100 . 45

= -4500

a, (-234) + |-145| + (-2019) + |155| + (-66)

= -234 + 145 - 2019 + 155 - 66

= (-234 - 66) + (145 + 155) - 2019

= -300 + 300 - 2019

= 0 - 2019

= -2019

b, -79 . |-45| - 21 . |45|

= -79 . 45 - 21 . 45

= 45 . ( -79 - 21 )

= 45 . (-100)

= -4500

aa) -(345+96345+96)+(−155+1996−155+1996)

=−345−96−155+1996=−345−96−155+1996

== (−345−155−345−155) - (96−199696−1996)

=−500+1900=−500+1900

=1400=1400

bb) (−456+95−456+95)-(-456+95456+95)-192192

=−456+95+456−95−192=−456+95+456−95−192

== (−456+456−456+456) + (95−9595−95) -192192

=−192=−192

cc) (a−b+ca−b+c)- (c−bc−b)+aa

=a−b+c−c+b+a=a−b+c−c+b+a

== (a+aa+a) + (−b+b−b+b) + (c−cc−c)

=2a=2a

dd)-(a−b+ca−b+c)+(c−bc−b)+aa

=−a+b−c+c−b+a=−a+b−c+c−b+a

== (−a+a−a+a) + (b−bb−b) + (−c+c−c+c)

=0=0

ee) (a−b+ca−b+c)+(c−bc−b)+aa

=a−b+c+c−b+a=a−b+c+c−b+a

== (a+aa+a) + (−b−b−b−b) + (c+cc+c)

=2a−2b+2c

sao có những chỗ liên tiếp vậy bn?

Bài 7: Thực hiện phép tính (tính hợp lí nếu có thể)

a) 78 349 – 10 240 + 56 711

= ( 78 349  + 56 711 ) – 10 240

=  635060 - 10240

=  624820

b) 234. 66 + 54. 80

=  15444 + 4320

= 19760

c) 13. 89 – 43. 17 + 339. 7

=  1157 - 731 + 2373

=  (1157 + 2373) - 731 

= 3530 - 731

=  2799

d) 2 085 – 1 196 : 26

=  2 085 – 46

=  2039

e) 214. 72 – 45. 214 – 214.27

= 214.( 72 – 45 – 27 )

= 214 . 0

= 0

\(a,=68109+56711=124820\)

\(b,=15444+4320=10764\)

\(c,1157-731+2373=426+2373=2799\)

\(d,=2085-46=2039\)

\(e,214.\left(72-45-27\right)=214.\left(-20\right)=-4200\)

\(g,=8327-1179=7148\)

\(h,=1225-1179=46\)

\(i,2304+1696=4000\)

\(k,=840+30+630=1500\)

\(m,456\left(123+321\right)-256=456.444-256=202464-256=202208\)

2.1256-{234-[-456+(-543-3.1256)]}

=2.1256-{234-[-456+(-543-3768)]}

=2.1256-{234-[-456+(-4311)]}

=2.1256-{234-(-4767)}

=2.1256-5001

=2512-5001

= -2489

:))^^^ TK MK NHA!!!!

đáp án là -2489

tao biết giải nhưng ko nói

|x-155|=-223+456

=> |x-155|=233

+) x-155=233

=> x=233+155

=> x=388

+) x-155=-233

=> x=-233+155

=> x=-78

Vậy x \(\in\){-78; 388}.

|x-155|=-223+456

|x-155|=233

=>|x-155|=+233

TH1:

x-155=233

x=233+155

x=388

TH2:

x-155=-233

x=-233+155

x=-78

Vay :x=388 hoac -78