Question

tính hợp lí b23. ( 145 – 17) – 145.( 23 -6) c) -38.( 25 - 4) + 25.(- 4 + 38) d) 24.(15 - 4) +4.(24 – 15) e) -39.(5 – 99) +99.(10 – 39)

giải thích r ạ 

Answer 1

giúp mk vs mk đng cần rất gấp!!

Answer 2

b, 23.(145 - 17) - 145. (23 - 6) 

= 145.23 - 17.23 - 145.23 + 145.6

= (145.23 + 145.6) - (145.23 + 17.23)

= 145.(23 + 6) - 23.(145 + 17)

= 145.29 - 23.162

= 479

Answer 3

c, -38. (25 - 4) + 25. (-4 + 38)

= (-38).25 - 4.(-38) + 25. (-4) + 25.38

= [(-38).25 - 4.(-38)] + [25. (-4) + 25.38]

= (-38).(25 - 4) + 25. [(-4) + 38]

= (-38). 21 + 25.34

= - 798 + 850

= 52

Answer 4

d, 24. (15 - 4) + 4. (24 - 15)

= 24.15 - 24.4 + 4.24 - 4.15

= 24.15 - 4.15

= 15. (24 - 4)

= 15.20

= 300

 

Answer 5

e, -39. (5 - 99) + 99. (10 - 39)

= -39.5 - 99.(-39) + 99.10 - 39.99

= [-39.5 - 99. (-39)] + (99.10 - 39.99)

= (-39).(5 - 99) + 99.(10 - 39)

= (-39). (-94) + 99.(-29)

= 795