\(=\dfrac{2}{35}\cdot\dfrac{3}{7}\cdot\dfrac{9}{7}=\dfrac{54}{1715}\)
\(2\cdot\dfrac{1}{5}\cdot\dfrac{1}{7}\cdot\dfrac{3}{7}\cdot\dfrac{9}{7}=\dfrac{2.1.1.3.9}{5.7^3}=\dfrac{54}{1715}\)
\(=\dfrac{2}{35}\cdot\dfrac{3}{7}\cdot\dfrac{9}{7}=\dfrac{54}{1715}\)
\(2\cdot\dfrac{1}{5}\cdot\dfrac{1}{7}\cdot\dfrac{3}{7}\cdot\dfrac{9}{7}=\dfrac{2.1.1.3.9}{5.7^3}=\dfrac{54}{1715}\)
Tính nhanh B= 1/5 -3/7 +5/9 -2/11+7/13-9/16-7/13+2/11-5/9+3/7 -1/5
Tính nhanh:
B = 1/5 - 3/7 + 5/9 - 2/11 + 7/13 - 9/16 -7/13 + 2/11 - 5/9 + 3/7 - 1/5
Thực hiện phép tính sau có thể
1.12/21-3/7+-2/3
2.-3/5+(-2/5+2)
3.6/7×10/9+1/7×10/9-8/9
4.5/7×5/11+5/7×2/11-5/7×14/11
A= (9 - 3/5 +2/3) - (7+ 7/5 - 3/2) - (3 - 9/5 + 5/2)
tính nhanh
1. Tính hợp lí:
a) B = 1/2 - [ 3/8 + ( -7/4 ) ]
b) -4/12 - ( -13/39 - 0,25 ) + 0,75
c) 1/2 - 1/3 + 1/23 + 1/6
d) ( -13/7 - 4/9) - ( -10/7 - 4/9 )
e) ( 7/8 - 5/2 + 4/7 ) - ( -3/7 + 1 - 13/8 )
f) -3/7 + ( 3 - 3/4 ) - ( 2,25 - 10/7)
g) ( 5/3 - 3/7 + 9 ) - ( 2 + 5/7 - 2/3 ) + ( 8/7 - 4/3 - 10 )
Tính hợp lý: A = (5/3-3/7+9)-(2+5/7-2/3)+(8/7-4/3-10)
tính A=1/3-3/5+5/7-7/9+9/11-11/13-9/11+7/9-5/7+3/5-1/3
tính nhanh A=1/3-3/4-(-3/5)+1/72-2/9-1/36+1/15
B=1/5-3/7+5/9-2/11+7/13-9/6-7/13+2/11-5/9-3/7-1/5
C1/100-1/100.99-1/99.98-1/98.87-...-1/3.2-1/2.1
Tính giá trị của biểu thức : 1*2*3+2*3*4+3*4*5+4*5*6+5*6*7+6*7*8+7*8*9+8*9*10