a) \(9\cdot8\cdot14+6\cdot\left(-17\right)\cdot\left(-12\right)+19\cdot\left(-4\right)\cdot18\)

\(=1008+1224-1368\\ =864\)

b) \(1-2+3-4+5-...+2015\)

\(=\left(1-2\right)+\left(3-4\right)+...+\left(2013-2014\right)+2015\) (1007 ngoặc đơn)

\(=-1-1-1-..-1+2015\)

\(=-1\cdot1007+2015\\ =-1007+2015\\ =1008\)

a) =9x8x14+6x17x12+19x18x(-4)

    =3x3x2x2x2x2x7+2x2x2x3x3x17-19x3x3x2x2x2

    =2x2x2x3x3x(2x7+17-19)

    =72x12

    =864

a) \(4.5^2-32:2^5\)

\(=4.25-2^5:2^5\)

\(=100-1\)

\(=99.\)

b) \(9.8.14+6.\left(-17\right)\left(-12\right)+19.\left(-4\right).18\)

\(=9.2.4.14+6.3.\left(-4\right)\left(-17\right)+76.18\)

\(=18.56+18.68+18.76\)

\(=18\left(56+68+76\right)\)

\(=18\left(132+68\right)\)

\(=18.200\)

\(=3600.\)

c) \(\left(\dfrac{-1}{2}\right)^3-2.\left(\dfrac{-1}{2}\right)^2+3.\left(\dfrac{-1}{2}\right)+1\)

\(=\left(\dfrac{-1}{2}\right)\left[\left(\dfrac{-1}{2}\right)^2+2.\dfrac{-1}{2}+3\right]+1\)

\(=\left(\dfrac{-1}{2}\right)\left[\dfrac{1}{4}+\left(-1\right)+3\right]+1\)

\(\)\(=\left(\dfrac{-1}{2}\right)\left[\dfrac{1}{4}+2\right]+1\)

\(=\left(\dfrac{-1}{2}\right).\dfrac{9}{4}+1\)

\(=\dfrac{-9}{8}+1\)

\(=\dfrac{-1}{8}\)

Bài 1.

Đặt (12n + 1; 30n + 2) = d

\(\Rightarrow\) \(\left\{{}\begin{matrix}12n+1⋮d\\30n+2⋮d\end{matrix}\right.\) \(\Rightarrow\) \(\left\{{}\begin{matrix}5\left(12n+1\right)⋮d\\2\left(30n+2\right)⋮d\end{matrix}\right.\) \(\Rightarrow\) \(\left\{{}\begin{matrix}60n+5⋮d\\60+4⋮d\end{matrix}\right.\)

\(\Rightarrow\) (60n + 5) - (60n + 4) \(⋮\) d

\(\Rightarrow\) 1 \(⋮\) d

\(\Rightarrow\) d = 1

\(\Rightarrow\) (12n + 1; 30n + 2) = 1

Vậy phân số \(\dfrac{12n+1}{30n+2}\) là phân số tối giản

\(8.9.14+6.17.12+19.4.18\)

\(=4.2.9.14+6.3.17.4+19.4.18\)

\(=4.18.14+18.4.17+19.4.18\)

\(=4.18.\left(14+17+19\right)\)

\(=4.18.50\)

\(=3600\)

- Tính nhẩm các phép tính trong phạm vi 20.

- Cộng hoặc trừ các số theo thứ tự từ phải sang trái.

4 + 2 = 6     10 - 6 = 4     3 + 4 = 7     14 + 4 = 18

8 - 5 = 3     19 + 0 = 19     2 + 8 = 10     18 - 5 = 13

3 + 6 = 9     17 - 6 = 11     10 - 7 = 3     12 + 7 = 19

hỏi máy con nhà bà tính

= 3600

= 864 tk nha mk nhanh nhất