Toán 5A.Tính nhanh a, 101$^{3}$ b, 47$^{3}$ +9 . 47$^{2}$ + 27 . 47 + 27 c, 299$^{3}$ d, 18$^{3}$ – 3 . 18$^{2}$ . 8$^{2}$ – 2$^{9}$ 14/07/2021 By Mackenzie 5A.Tính nhanh a, 101$^{3}$ b, 47$^{3}$ +9 . 47$^{2}$ + 27 . 47 + 27 c, 299$^{3}$ d, 18$^{3}$ – 3 . 18$^{2}$ . 8$^{2}$ – 2$^{9}$
Đáp án: 5.Tính nhanh a) `101^3` = `(100+1)^3` = `100^3 + 3.100^2.1 +3. 100 .1^2 + 1^3` = `1000000 + 30000 + 300 +1` = `1030301` b) ` 47^3 + 9. 47^2 + 27 . 47 +27` = ` 47^3 + 3 . 3 .47^2 + 3 .3^2 .47 +3^3` = `(47+3)^3` = ` 50^3` = ` 125 000` c) ` 299^3` = `(300-1)^3` = `300^3- 3.300^2.1 +3.300.1^2 -1^3` = `27000000 – 270000 + 900 -1` = `26 730 899` d) `18^3 – 3 . 18^2 . 8 + 3 . 18 . 8^2 – 2^9` = ` 18^3 – 3. 18^2 .8 + 3 . 18 . 8 ^2 – 8^3` = ` (18-8)^3 = 10^3 = 1000` Trả lời
Đáp án: $a, 101³ $ $= (100 + 1)³ $ $= 100³ + 3.100² + 3.100 + 1$ $= 1000000 + 30000 + 300 + 1$ $= 1030301$ $b, 47³ + 9 . 47² + 27 . 47 + 27 $ $= 47³ + 3.3.47² + 3.3².47 + 3³ $ $= (47 + 3)³ $ $= 50³ $ $= 12500 $ $c, 299³ $ $= (300 – 1)³ $ $= 300³ – 3.300² + 3.300 – 1 $ $= 27000000 – 27000 + 900 – 1 $ $= 26973899 $ $d, 18³ – 3.18². 8 + 3.18 . 8² – $ $2^{9}$ $= 18³ – 3.18². 8 + 3.18 . 8² – 8³ $ $= (18 – 8)³ $ $= 10³ $ $= 1000$ Trả lời