A=(1+2+3+...+2021).(12+22+32+...+102).(2020.111-3.5.37.404) B=(-1)+(-5)+(-9)+...+(-101) C=(-1)+3+(-5)+7+...+(-2021)+2023 D =1-2+3-4+...+99-100 thực hiện phép tính
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P=[(1-2)+(-3+4)+(5-6)+(-7+8)+...+(993-994)+(-995+996)]+997
P=[(-1)+1+(-1)+1+...+(-1)+1+(-1)+1]+997
P= 0 +0 +...+ 0 +997
P=997
Bài 2:
a: \(\left(6x-39\right):7=3\)
\(\Leftrightarrow6x-39=21\)
hay x=10
a)1,5.(1/3-2/3)
=3/2.(-1/3)
=-1/2
b)2/5+3/5:(-3/2)=1/2
=2/3+2/5+1/2
=16/15+1/2
=47/30
c)1 và 2/5 - (-1/2)^2 + 7/10
=7/5 - 1/4 + 7/10
=23/20 + 7/10
=37/20
\(a,\dfrac{2}{7}+\dfrac{5}{7}.\dfrac{7}{10}-\dfrac{1}{14}\)
\(=\dfrac{1}{7}.2+\dfrac{1}{7}.5.\dfrac{7}{10}-\dfrac{1}{7}.\dfrac{1}{2}\)
\(=\dfrac{1}{7}.\left(2+\dfrac{35}{10}-\dfrac{1}{2}\right)\)
\(=\dfrac{1}{7}.\left(\dfrac{4}{2}+\dfrac{7}{2}-\dfrac{1}{2}\right)\)
\(=\dfrac{1}{7}.5=\dfrac{5}{7}\)
\(b,\left(3\dfrac{1}{2}-\dfrac{2}{3}\right).\dfrac{7}{34}-\dfrac{5}{34}\)
\(=\left(\dfrac{7}{2}-\dfrac{2}{3}\right).\dfrac{7}{34}-\dfrac{7}{34}.\dfrac{5}{7}\)
\(=\dfrac{7}{34}.\left(\dfrac{17}{6}-\dfrac{5}{7}\right)\)
\(=\dfrac{7}{34}.\dfrac{89}{42}=\dfrac{89}{204}\)
a: =2/7-1/14+5/10
=2/7-1/14+1/2
=4/14-1/14+7/14
=10/14=5/7
b: =(7/2-2/3)*7/34-5/34
\(=\dfrac{21-4}{6}\cdot\dfrac{7}{34}-\dfrac{5}{34}\)
\(=\dfrac{7}{6}\cdot\dfrac{1}{2}-\dfrac{5}{34}=\dfrac{7}{12}-\dfrac{5}{34}=\dfrac{89}{204}\)
a)= 2021.2021-2020.(2021+1)
= 2021.(2020+1)-2020.(2021+1)
= (2021.2020)+2021-(2020.2021)-2020
= 1
b) B= (1+2-3-4)+(5+6-7-8)+(9+10-11-12)...........+(2017+2018-2019-2020)+2021
B= -4+(-4)+....................(-4)+2021
B= -4x505+2021
B= -2020 + 2021
B = 1
a) 2021 - (1/3)² . 3²
= 2021 - 1/9 . 9
= 2021 - 1
= 2020
b) 5/10 + 9 . (-3/2)
= 1/2 - 27/2
= -26/2
= -13
c) -10 . (-2021/2022)⁰ + (2/5)² : 2
= -10 . 1 + 4/25 . 2
= -10 + 8/25
= -68/7
\(a,2021-\left(\dfrac{1}{3}\right)^2\cdot3^2\\ =2021-\dfrac{1}{9}\cdot9\\ =2021-\dfrac{9}{9}\\ =2021-1=2020\\ b,\dfrac{5}{10}+9\cdot\dfrac{-3}{2}\\ =\dfrac{5}{10}+\dfrac{-27}{2}\\ =\dfrac{5}{10}+\dfrac{-135}{10}\\ =-\dfrac{130}{10}\\ =-13\\ c,-10\cdot\left(-\dfrac{2021}{2022}\right)^0+\left(\dfrac{2}{5}\right)^2:2\\ =-10\cdot1+\dfrac{4}{25}\cdot\dfrac{1}{2}\\ =-10+\dfrac{4}{50}\\ =-10+\dfrac{2}{25}\\ =-\dfrac{248}{25}\)
Lời giải:
$A=(-1-2+3+4)+(-5-6+7+8)+(-9-10+11+12)+...+(-2021-2022+2023+2024)-2024$
$=\underbrace{4+4+...+4}_{506}-2024$
$=4.506-2024=0$
A = 0
B = -1326
C = 1012
D = -50
Câu A
A = (1+2 +...+ 2021).(12 + 22 + 32 + ...+ 102).(2020.111 - 3.5.37404)
A = (1 + 2 +...+ 2021).(12 + 22 + ...+ 102).[2020.111-(3.37).(5.404)]
A= (1+2+...+2021).(12+22 +...+102).(2020.111-111.2020)
A = (1+2+...+2021).(12 + 22 + ... + 102).0
A = 0