(17.85 + 15.17) + (-120)

= 17.85 + 15.17 + (-120)

= 17.(85 + 15) + (-120)

= 17.100 + (-120)

= 1700 + (-120)

= 1580

(17.85+15.17)+(-120)

=((17.(85+15))+(-120)

=17.100+(-120)

=1700+(-120)

=1580

giúp gì

?????

chứng tỏ 2+2^2+2^3+...+2^2023+2^2024

=(2+2^2+2^3+2^4)+(2^5+2^6+2^7+2^8)+(2^9+2^10+2^11+2^12)+.....+(2^2021+2^2022+2^2023+2^2024)

=30+2^5.(2+2^2+2^3+2^4)+2^9.(2+2^2+2^3+2^4)+.....+2^2021.(2+2^2+2^3+2^4)

=30+2^5.30+2^9.30+......+2^2021.30

=30.(1+2^5+2^9+....+2^2021) chia hết cho 5   (vì 30 chia hết cho 5)

vậy 2+2^2+2^3+....+2^2023+2^2024 chia hết cho 5

chill

2^x : 4 = 16

2^x = 16 x 4

2^x = 64

2^x = 2⁶

⇒ x = 6

2^x :4=16

2^x    =16x4

2^x    =64

2^x    =2^6

   x     =6

tớ nhầm ,là văn nhé

dài hay ngắn bạn

1 - 3  + 3² - 3³ + ... + (-3)^\(x\) = \(\dfrac{9^{1013}+1}{4}\)

Đặt vế trái bằng A ta có:

        A = 1 - 3   + 3² - 3³ + ... + (-3)^\(x\)

     3A =  3 - 3² + 3³ - 3⁴ + ... + (-3)^{\(^{x+1}\)}

3A + A =(3-3²+3³-3⁴+...+(-3)^{\(^{x+1}\)}+(1 - 3+...+(-3)^{\(^{x+1}\)}

4A      = 3 -3² + 3³-3⁴+...+(-3)^{\(^{x+1}\)}+ 1 - 3 + ... + (-3)^{\(^x\)}

4A = (3 -3) + (-3²+ 3²) +....+(3^{\(^x\)} + (-3)^{\(^x\)}) + (1 +  (-3)\(^{x+1}\))

4A =  0 + 0 +...+ 0 +0 + 1 + (-3)\(^{x+1}\)

A = \(\dfrac{1+\left(-3\right)^{x+1}}{4}\)

⇒ \(\dfrac{1+\left(-3\right)^{x+1}}{4}\) = \(\dfrac{9^{1013}+1}{4}\)

1 + (-3)\(^{x+1}\) = 9¹⁰¹³ + 1

     (-3)^{\(^{x+1}\)}  = 9¹⁰¹³

    (-3)^{\(^{x+1}\)} = (-3)^2.1013

       \(x\) + 1  = 2026

        \(x\)       = 2025 

Bài 1:
c. $\frac{-28}{4}\leq x\leq \frac{-21}{7}$

$\Rightarrow -7\leq x\leq -3$

$\Rightarrow x\in \left\{-7; -6; -5; -4; -3\right\}$
d.

\(\frac{153}{-9}\leq x\leq \frac{165}{-11}\\ \Rightarrow -17\leq x\leq -15\\ \Rightarrow x\in \left\{-17; -16; -15\right\}\)

Bài 2:

a. $\frac{2}{8}=\frac{9}{36}$

$\frac{2}{9}=\frac{8}{36}$

$\frac{8}{2}=\frac{36}{9}$

$\frac{9}{2}=\frac{36}{8}$

b.

$\frac{-2}{4}=\frac{7}{-14}$

$\frac{-2}{7}=\frac{4}{-14}$

$\frac{4}{-2}=\frac{-14}{7}$

$\frac{7}{-2}=\frac{-14}{4}$

c.

$\frac{-4}{12}=\frac{-2}{6}$

$\frac{-4}{-2}=\frac{12}{6}$

$\frac{12}{-4}=\frac{6}{-2}$

$\frac{-2}{-4}=\frac{6}{12}$

Bài toán: Tìm số nguyên $x$ thỏa mãn $15\vdots 2x+1$

-----------------

Lời giải:
$15\vdots 2x+1$

$\Rightarrow 2x+1\in Ư(15)$

$\Rightarrow 2x+1\in \left\{1; -1; 3; -3; 5; -5; 15; -15\right\}$

$\Rightarrow x\in \left\{0; -1; 1; -2; 2; -3; 7; -8\right\}$

Giúp đi màaa!!!8 giờ nộp bài r=((((((

Bài 1:

c. $\frac{-28}{4}\leq x\leq \frac{-21}{7}$

$\Rightarrow -7\leq x\leq -3$

$\Rightarrow x\in \left\{-7; -6; -5; -4; -3\right\}$

f.

$\frac{153}{-9}\leq x\leq \frac{165}{-11}$

$\Rightarrow -17\leq x\leq -15$

$\Rightarrow x\in \left\{-17; -16; -15\right\}$

Mik tên An, ny mik tên Bình nè! Hì