4 Tính nhanh:
2020 × 45 + 2020 × 54 + 2020
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Ta có: \(2020^{45}-2020^{44}\)
\(=2020^{44}\cdot2020-2020^{44}\cdot1\)
\(=2020^{44}\cdot\left(2020-1\right)\)
\(=2020^{44}\cdot2019\)
Ta có: \(2020^{44}-2020^{43}\)
\(=2020^{43}\cdot2020-2020^{43}\cdot1\)
\(=2020^{43}\cdot\left(2020-1\right)\)
\(=2020^{43}\cdot2019\)
Vì \(2020^{44}>2020^{43}\)
nên \(2020^{44}\cdot2019>2020^{43}\cdot2019\)
hay \(2020^{45}-2020^{44}>2020^{44}-2020^{43}\)
A) 23 + [(-3) - (-7)] - [ -8 + (-9) - 5]
= 23 + [ - 3 + 7 ] - [ - 8 - 9 - 5 ]
= 23 + 4 - [ - 22]
= 27 + 22
= 49
B)( 2020 + 54) - (2020 - 46)
= 2020 + 54 - 2020 + 46
= ( 2020 - 2020 ) + ( 54 + 46 )
= 0 + 100
= 100
Học tốt
@Chiyuki Fujito.
Tính nhanh
2020×28+74×2020-4040
= 2020 x 28 + 74 x 2020 - 2020 x 2
= 2020 x (28+74 - 2)
= 2020 x 100
= 202 000
I don't now
sorry
...................
nha
2019 . 2021 - 2020. 2020
= 2019(2020+1) - 2020( 2019+1)
= 2019 .2020 + 1.2019 - 2020.2019 + 1.2020
= 2019 -2020
= -1
\(2019.2021-2020.2020\)
\(=2019\left(2020+1\right)-2020\left(2019+1\right)\)
\(=2019.2020+2019-2020.2019+2020\)
\(=2019-2020\)
\(=-1\)
2020 × 45 + 2020 × 54 + 2020
= 2020 × 45 + 2020 × 54 + 2020 x 1
= 2020 x ( 45 + 54 + 1 )
= 2020 x 100
= 202 000
\(2020\times45+2020\times54+2020\)
\(=2020\times\left(45+54+1\right)\)
\(=2020\times100\)
\(=202000\)