Ta có: \(\frac{4^2}{20.24}+\frac{4^2}{24.28}+...+\frac{4^2}{76.80}\)

\(=4.\left(\frac{4}{20.24}+\frac{4}{24.28}+...+\frac{4}{76.80}\right)\)

\(=4.\left(\frac{1}{20}-\frac{1}{24}+\frac{1}{24}-\frac{1}{28}+...+\frac{1}{76}-\frac{1}{80}\right)\)

\(=4.\left(\frac{1}{20}-\frac{1}{80}\right)=4.\frac{3}{80}=\frac{3}{20}< 1\)

Vậy \(\frac{4^2}{20.24}+\frac{4^2}{24.28}+...+\frac{4^2}{76.80}< 1\)

ấn máy cho nhanh

đề ko yêu cầu tính nhanh mà ta, 

a)(2x+4).8-40=24

(2x+4).8=24+40

(2x+4).8=64

2x+4=64:8

2x+4=8

2x=8+4

2x=12

x=12:2

x=6

b)(2x+4²)-8=64:2

(2x+16)-8=32

2x+16=32+8

2x+16=40

2x=40-16

2x=24

x=24:2

x=12

c)(3x+2).4-20=24

(3x+2).4=24+20

(3x+2).4=44

3x+2=44:4

3x+2=11

3x=11-2

3x=9

x=9:3

x=3

24¹² : 24¹² + 2 . 2² - 9⁴ : 9³ + 5⁰ .16

= 1 + 2^3 - 9 + 16

= 1 +8 -9 +16

= 16

\(24^{12}:24^{12}+2.2^2-9^4:9^3+5^0.16\)

\(=1+2^3-9+1.16\)

\(=1+8-9+16\)

\(=16\)

Ủng hộ nha

=1+8-9+16 = 16

24¹² : 24¹² + 2 . 2² - 9⁴ : 9³ + 5⁰ . 16=16

k nha

A = 4+4²+4³+...+4²⁴ ( Có 24 số hạng )

A = (4+4²) + (4³+4⁴) + ... + (4²³+4²⁴)     ( Có 12 cặp )

A = 20 + 4².(4+4²) + ... + 4²².(4+4²)

A = 20 + 4².20 + ... + 4²².20 \(⋮\)20

\(\Rightarrow\)A \(⋮\)20 (đpcm)

Đặt A= 4+4²+4³+...+4²³+4²⁴

​=> 4A= 4^​2+4³+4⁴+...+4²⁴+4²⁵

=> 4A-A = 4²⁵​ - 4

​=> 3A = 4²⁵​ - 4

​=> A = ( 4^​25​ - 4) : 3

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Trả lời

2⁴.17-16.24+2⁴.9

=2⁴.(17+9)-16.24

=16.26-16.24

=16.(26-24)

=16.2

=32 !

A = 4 + 4² + 4³ + ... + 4²⁴
= (4 + 4²) + (4³ + 4⁴) + ... + (4²³ + 4²⁴)
= 20 + 4²(4 + 4²) + ... + 4²²(4 + 4²)
= 20 + 4².20 + ... + 4²².20
= 20.(1 + 4² + ... + 4²²) \(⋮20\)
@PARTICULARLY JUST ME

thanks bạn nha