BÀi 1:

a: (-243+345)-(257+(-55)-129)

=-243+345-257+55+129

=(-243-257)+(345+55)+129

=-500+400+129

=-100+129

=29

b: \(\left(-2\right)^3-45:\left(-3\right)^2-\left(-2019\right)^0\cdot\left(-1\right)^{2019}\)

\(=-8-\frac{45}{9}-1\cdot\left(-1\right)\)

=-8-5+1

=-13+1

=-12

c: \(\left\lbrack27\cdot\left(-67\right)+33\cdot\left(-27\right)\right\rbrack:\left(-30\right)\)

\(=\frac{-27\left(67+33\right)}{-30}\)

\(=\frac{9}{10}\cdot100=90\)

d: \(\left(1^2+2^2+\cdots+100^2\right)\left(3^4-9^2\right)\)

\(=\left(1^2+2^2+\cdots+100^2\right)\left(81-81\right)\)

=0

e: \(53\cdot47+53^2-2021^0\)

\(=53\left(53+47\right)-1\)

=5300-1

=5299

i: 38+(-21)+(-58)+(-6)

=(38-58)+(-21-6)

=-20-27

=-47

h: (2020+27)-[2020+(-73)]-129

=2020+27-2020+73-129

=100-129

=-29

Lời giải:

$A=(-1-2+3+4)+(-5-6+7+8)+(-9-10+11+12)+...+(-2021-2022+2023+2024)-2024$

$=\underbrace{4+4+...+4}_{506}-2024$
$=4.506-2024=0$

Mik làm luôn, ko vt lại đề

B = 1/1 - 1/3 + 1/3 - 1/5 +...+1/2017 - 1/2019

B = 1 - 1/2019

B = 2018/2019

TL:

\(B=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{2017}-\frac{1}{2019}\) 

\(B=1-\frac{1}{2019}\) 

\(B=\frac{2018}{2019}\) 

Vậy \(B=\frac{2018}{2019}\)

1-3-5+7+9-11-13+15+...+2017-2019-2021+2023=

=(1-3-5+7)+(9-11-13+15)+...+(2017-2019-2021+2023)=
=0+0+.....+0=0

=2019

Viết lại hộ mik cái

Ko nhìn đc bn ui!@##

bạn viết gì vậy

=(2015/ 2019 + 3/2019 + 1/2019 ) : 1/2

= 2019/2019 x 2

= 1 x2 

=2

2015/2019:1/2+3/2019:1/2+1/2019:1/2

=(2015/2019+3/2019+1/2019):1/2

=1:1/2

=2

k cho mink nha

2. Tìm x:

( x - 3 )² - x + 3 = 0

=> x² - 6x + 9 - x + 3 = 0

=> x² - 7x + 12 = 0

=> ( x² - 3x ) + ( 4x - 12 ) = 0

=> x.(x - 3) + 4.(x - 3) = 0

=> ( x - 3 ).( x + 4 ) = 0

=> x - 3 = 0 => x = 3

     x + 4 = 0 => x = -4

Trl:

1.

a. \(75^2+150\text{.}25+25^2\)

\(=75^2+2\text{.}75\text{.}25+25^2\)

\(=\left(75+25\right)^2\)

\(=100^2\)

\(=10000\)

b. \(2019^2-2019.19-19^2-19.1981\)

(Đề bài có sai ko vậy???)~ hoặc lak do mk ngu quá k bt lm

2. \(\left(\text{x}-3\right)^2-\text{x}+3=0\)

\(\text{x}^2-6\text{x}+9-\text{x}+3=0\)

\(\text{x}^2-7\text{x}+12=0\)

\(\text{x}^2-3\text{x}-4\text{x}+12=0\)

\(\text{x}\left(\text{x}-3\right)-4\left(\text{x}-3\right)=0\)

\(\left(\text{x}-3\right)\left(\text{x}-4\right)=0\)

\(\orbr{\begin{cases}\text{x}-3=0\\\text{x}-4=0\end{cases}\Leftrightarrow\orbr{\begin{cases}\text{x}=3\\\text{x}=4\end{cases}}}\)

Vậy ....

#HuyềnAnh#

1954 - 2 . ( 2019 + 977 ) + ( 4038 - 5421 ) + 4421.

= 1954 - 4038+ 1954 + 4038 - 5421 + 4421

= 1954 + 1954 - 421 + 421 + 5000 + 4000

= 2. 1945 + 9000

=3908

xl mik chưa lm xong

Ta có:

C=2019-2-4-6-...-100

  =2019-(2+4+6+...+100)

Đặt B=2+4+6+...+100(1)

Tổng B có số số hạng là:

(100-2):2+1=50(số hạng)

Cứ nhóm 2 số vào 1 nhóm

=> có tất cả:50:2=25(nhóm)

Khi đó (1) có dạng:

B=(2+100)+(4+98)+...+(50+52)

  =102+102+...+102

  =102.25

  =2550

Thay B=2550 vào C=2019-(2+4+6+...+100),ta có:

C=2019-2550=2019+(-2550)= -531

Vậy C= -531

Chúc bạn hok tốt,bạn nhớ k đúng cho mik na!!!

    \(2^3-45:\left(-3\right)^2+\left(-2019\right)^0\cdot\left(-1\right)^{2019}\)
\(=8-45:9+1\cdot\left(-1\right)\)
\(=8-5+\left(-1\right)\)
\(=3+\left(-1\right)\)
\(=2\)

\(PeaGea\)

(2)³ - 45 : (-3²) + (-2019)⁰ . (-1)²⁰¹⁹

= 8 - 45 : 9 + 1 . (-1)

= 8 - 5 + (-1)

= 3 + (-1)

= 2