A 12x56 + 12x44 =44+56=100

100X56=5600

b 45x12-45x2+45x90=90+2-12=80

80x45=3600

a) 12 x 56 + 12 x 44

=12.(56+44)

=12.100

=1200

b) 45 x 12 - 45 x 2 + 45 x 90

=45.(12-2+90)

=45.100

=4500

a)12x56+12x44

=12(56+44)

=12x100

=1200

b)45x12-45x2+45x90

=45(12-2+90)

=45x100

=4500

271+31+29 + 69=

= (271+29)+

250                   57

150                   -337

a)223-(-27)=250   

12-(-45)=57

44-(-106)=-62

-410-(-73)=-337

a, Ta có: 3³⁹ < 3⁴⁰ = (3²)²⁰ = 9²⁰

11²¹ > 11²⁰

Vì 9 < 11 => 9²⁰ < 11²⁰ => 3³⁹ < 11²¹

b, Ta có: 12⁴⁵ - 12⁴⁴ = 12⁴⁴(12 - 1) = 12⁴⁴.11

12⁴⁴ - 12⁴³ = 12⁴³(12 - 1) = 12⁴³.11

Vì 12⁴⁴ > 12⁴³ => 12⁴⁴.11 > 12⁴³.11 => 12⁴⁵ - 12⁴⁴ > 12⁴⁴ - 12⁴³

c, Đặt A = 1+2+2²+....+2⁹

2A = 2+2²+2³+...+2¹⁰

2A-A=2¹⁰-1

A=2¹⁰-1

Ta có: 5.2⁸ = 2⁸.4 > 2⁸.4 - 1 = 2¹⁰ - 1

Vậy A < 5.2⁸

B=5(1/12−1/21+1/21−1/30)−5(1/24−1/34+1/34−1/44+1/44−1/54+1/54−1/64)

B=5(1/12−1/21+1/21−1/30+1/24−1/34+1/34−1/44+1/44−1/54+1/54−1/64 )

B=5(1/12−1/64)=5.13/192=65/192

Đáp án :\(\frac{65}{192}\)

B=65/192

c,65

like nha b

A

A. 41; 43; 45; 47; 49.

12+44+45+56+55+88+91+27+9+73

=(12+88)+(44+56)+(45+55)+(91+9)+(27+73)

=   100   +   100   +   100  +  100   +   100

=              100    x    5

=                     500

Chúc bạn học tốt!

Trả lời : 

=500

ủng hộ nha

(12 +88) + (44 + 56) + (45 + 55) + (91 + 9) + (27 +73) = 500