$A=(-135)\cdot29-13\cdot135+42\cdot(-65)$

$=(-135)\cdot29+13\cdot(-135)+42\cdot(-65)$

$=(-135)\cdot(29+13)+42\cdot(-65)$

$=(-135)\cdot42+42\cdot(-65)$

$=42\cdot(-135-65)$

$=42\cdot(-200)$

$=-8400$

A = (-135). 29 - 13. 135 + 42. (-65)

A = 135. (-29) - 13. 135 + 42. (-65)

A = 135. [(-29) - 13] + 42. (-65)

A = 135. (-42) + 42. (-65)

A = 135. (-42) + (-42). 65

A = (-42). (135 + 65)

A = (-42). 200

A = -8400

\(=\left(-3915\right)-1755+\left(-2730\right)=-8400\)

= ( - 29) . 135 + 13 . 135 +( - 2730)

= 135 . [ ( - 29) + 13] + ( - 2730)               mik nghĩ là như này

= 135 . ( - 16) + ( - 2730)

= ( - 2160) + ( - 2730)

= - 4890                                  

Các bạn nhớ ghi cách làm ra nhé!

a) 67+135+33=(67+33)+135=100+135=235

b) 277+13+323+87=(277+323)+(113+87)=600+200=800

c) 29+132 + 237 + 868 + 763=29+(132+868)+(237+763)=29+1000+1000=2029

d) 652 + 327 + 148 + 15 + 73=(652+148)+(327+73)+15=800+400+15=1215

e) 463 + 318 + 137 + 22=(463+137)+(318+22)=600+340=940

g) 189 + 424 +511 + 276 + 55=(189+511)+(424+276)+55=700+700+55=1455

h) (321 +27) + 79=(321+79)+27=400+27=427

i) 185+434+515+266+155=(185+515)+(434+266)+155=700+700+155=1555

k) 168 + 79 + 132=(168+132)+79=300+79=379

l) 29 + 132 + 237 + 868 + 763=29+(132+868)+(237+763)=29+1000+1000=2029

A. - 279.    B. -170.      C. -4600.      D. -4200

a) \(42+37+135+58+63=\left(42+58\right)+\left(37+63\right)+135=100+100+135=335\)

b) \(25.17.8.4.125=\left(25.4\right).\left(8.125\right).17=100.1000.17=1700000\)

c) \(43.27+93.43+57.61+59.57=43.\left(27+93\right)+57.\left(61+57\right)=43.120+57.120\)

\(=120.\left(43+57\right)=120.100=12000\)

d) \(64.6+81.4+17.6=6.\left(64+17\right)+81.4=6.81+81.4=81.\left(6+4\right)=81.10=810\)

e) \(1+11+21+31+...+991=\left(991+1\right).\left[\left(991-1\right)\div10+1\right]\div2\)

\(=992.\left[990\div10+1\right]\div2=496.\left[99+1\right]=496.100=49600\)

117 +68 + 23 = (117 +23) + 68 = 140 + 68 = 208.

117 + 68 + 23.

=(117+23)+68

=140+68

=208

117+68+23

=  117+ (68+23) 

=117+91

=208

256/33

chúc bạn học tốt

\(\frac{11}{12}+\frac{19}{20}+\frac{29}{30}+\frac{41}{42}+\frac{55}{56}+\frac{71}{72}+\frac{89}{90}+\frac{109}{110}\)

\(=1-\left(\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}+\frac{1}{72}+\frac{1}{90}+\frac{1}{110}\right)\)

\(=1-\left(\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}+\frac{1}{8.9}+\frac{1}{9.10}+\frac{1}{10.11}\right)\)

\(=1-\left(\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}+\frac{1}{9}-\frac{1}{10}+\frac{1}{10}-\frac{1}{11}\right)\)\(=1-\left(\frac{1}{3}-\frac{1}{11}\right)=1-\frac{8}{33}=\frac{25}{33}\)