a) Ta có: \(1+\left(-2\right)+3+\left(-4\right)+...+2021\)
\(=\left(1-2\right)+\left(3-4\right)+...+\left(2019-2020\right)+2021\)
\(=\left(-1\right)+\left(-1\right)+...+\left(-1\right)+2021\)
\(=-1010+2021=1011\)
1.Tính
a) 1 + (-2)+3+(-4)+......+2021
1 . Tính
a) -27/5 . -4/15 + -4/15 . ( 2021 - 27/5)
1 . Tính
a) -27/5 . -4/15 + -4/15 . ( 2021 - 27/5)
1 . Tính
a) -27/5 . -4/15 + -4/15 . ( 2021 - 27/5)
1 . Tính
a) -27/5 . -4/15 + -4/15 . ( 2021 - 27/5)
Bài 1: tính
a. 1/3-(-1và2/5)+(-3và1/4)
b.5/4-(-3và1/2)-7/10
c.3/2-[(-4/7)-(1/2+5/8)]
Câu 24: Cho biểu thức: A=1/2+1/3+1/4+.........+1/2021+1/2022 Và B=2021/1+2020/2+2019/3+.........+3/2019+2020+1/2021
bài 1. Tính
a) 7/-25 + -8/25 b) 6/13 + -15/39 c) 5/7 + 4/-14 d) -8/18 + -15/27
bài 2. Tính
a) 3/5 + -7/4 b) (-2) + -5/8 c) 1/8 + -5/9 d) 6/13 + -14/39 e) -18/24 + 15/21
bài 14: tính
a,\(\dfrac{4}{5}\) + \(\dfrac{1}{4}\) x \(\dfrac{2}{3}\)
b,\(\dfrac{7}{12}\) + \(\dfrac{3}{4}\) : \(\dfrac{3}{8}\) - \(\dfrac{1}{4}\)
