a, (- 40 - 16 + 32 ) + ( 40 + 116 - 32 )

=( - 40 )- 16 + 32 + 40 + 116 - 32

=[(-40)+40]+32-32+116-16

=0+ (32-32)+(116-16)

=0+0+100

=100

b, -15 + 5 + ( 20 - 100 - 2017 ) - ( - 15 - 2017 )

=  -15 + 5 + 20 - 100 - 2017 + 15 + 2017 

=[(-15 )+ 15] + (2017 - 2017 ) + 20-100

=0+0+(20-100)

= - 80

A) (12/24 + 24/32 - 5/20) : 4/5

   = (1/2 + 3/4 - 1/4) : 4/5

   =(1/2 + 1/2) : 4/5

   =     1        : 4/5 

   =           5/4

B) 75/100 + 1/5 - 11/3 + 25/100

    = 3/4    + 1/5 - 11/3 + 1/4

    = (3/4 + 1/4) - 1/5+11/3

    =       1        -  1/5 + 11/3

    =             4/5        +  11/3

    =             67/15

   ( mk ko chắc câu B) 

Vì N<1

=> N= 20^31+2/20^32+2

<20^31+2+38/ 20^32+2+38

=20^31+40/ 20^32+40

=20.(20^30+2) / 20.(20^31+2)

=20^30+2 / 20^32+2 = M

Vậy N<M

\(N=\frac{20^{31}+2}{20^{32}+2}=\frac{20^{31}+2+18}{20^{32}+2+18}=\frac{20^{31}+20}{20^{32}+20}=\frac{10.\left(20^{30}+2\right)}{10.\left(20^{31}+2\right)}\)\(=M\)

\(\Rightarrow M=N\)
 

Ta thấy:

A < 1

B >1

=> A > B

đặt B = 1+2²+2³+2⁴+...+2³⁰

=> 2B = 2²+2³+2⁴+...+2³¹

=> 2B-B = ( 2²+2³+2⁴+...+2³¹ ) - ( +2²+2³+2⁴+...+2³⁰ )

=> 1B = 2³¹ - 1

\(\Rightarrow1B=\frac{2^{31}-1}{1}\)

lộn làm lại nhé ^^ :

Đặt B = 1 + 2² + 2³ + 2⁴ + ... + 2²⁰

=> 2B = 2² + 2³ + 2⁴ + ... + 2²¹

=> 2B - B = ( 2² + 2³ + 2⁴ + ... + 2²¹ ) - ( 1 + 2² + 2⁴ + ... + 2²⁰ )

=> 1B = 2²¹ - 1

\(\Rightarrow1B=\frac{2^{21}-1}{1}\)

7x5⁹⁸ + 5¹⁰⁰ / 32

= 5⁹⁸ x ( 7 + 5²) / 32

= 5⁹⁸ x ( 7 + 25) / 32

= 5⁹⁸ x 32 / 32

= 5⁹⁸

7x5⁹⁸ + 5¹⁰⁰ / 32

= 5⁹⁸ x ( 7 + 5²) / 32

= 5⁹⁸ x ( 7 + 25) / 32

= 5⁹⁸ x 32 / 32

= 5⁹⁸

Có lời giải đàng hoàng nha