Question

Tính hợp lí: 
a, 3,4 - 4,5 + 1,6 - 10,5
b, 4,2 . 5,92 + 4,2 . 5,08 - 4,2
c, A = 1 + (-3) + 5 + (-7) + ....... + 21 + (-23)
d, B = (-1) + 2 + (-3) + 4 + (-5) + 6 + ...... + (-2021) + 2022
Ai giúp em với ạ!

Answer 1

a) \(3,4-4,5+1,6-10,5\)

\(=\left(3,4+1,6\right)-\left(4,5+10,5\right)\)

\(=5-14=-9\)

b) \(4,2.5,92+4,2.5,08-4,2\)

\(=4,2\left(5,92+5,08-4,2\right)\)

\(=4,2.10=42\)

c) \(A=1+\left(-3\right)+5+\left(-7\right)+...+21+\left(-23\right)\)

\(=\left(1-3\right)+\left(5-7\right)+...+\left(21-23\right)\)

\(=-2.\left(-2\right).....\left(-2\right)\)

\(=12\)

d) \(B=\left(-1\right)+2+\left(-3\right)+4+...+\left(-2021\right)+2022\)

\(\Rightarrow B=\left(2-1\right)+\left(4-3\right)+...+\left(2022-2021\right)\)

\(\Rightarrow B=1+1+1+...+1\)

\(\Rightarrow B=2022\)