so sánh với 0 , bn nhé

từng số ss với 0 hay là nhân?

nhìn là biết rồi,cái bên trái

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

\(A=2^{2019}-\left(2^{2018}+2^{2017}+2^{2016}+.....+2^1+2^0\right)\)

Đặt: \(B=2^{2018}+2^{2017}+2^{2016}+....+2^1+2^0\)

\(\Rightarrow2B=\left(2^{2018}+2^{2017}+2^{2016}+...+2^1+2^0\right)\)

\(\Rightarrow2B-B=\left(2^{2019}+2^{2018}+2^{2017}+...+2^2+2\right)-\left(2^{2018}+2^{2017}+2^{2016}+...+2^1+2^0\right)\)

\(\Rightarrow B=2^{2019}-1\)

\(\Rightarrow A=2^{2019}-\left(2^{2018}+2^{2017}+2^{2016}+.....+2^1+2^0\right)\)

\(=2^{2019}-\left(2^{2019}-1\right)=2^{2019}+2^{2019}+1>1\)

đoạn cuối cùng bạn làm sai rồi

S=1+(2-3)+(-4+5)+(6-7)+(-8+9)+...+(-2020+2021)
S=1-1+1-1+1+...+1
S=1+0+0+...+0
S=1

\(3a=3+\frac{1}{3}+\frac{1}{3^2}+...+\frac{1}{3^{2018}}\)

\(2a=3a-a=3-\frac{1}{3}-\frac{1}{3^{2019}}< 3\Rightarrow a< \frac{3}{2}\)

bài 1:

ssh của A là:

(151-3):2+1=75

A=(151+3)x75:2=5775

đáp số: 5775