=[12+(-12)]+[(-6)-(-6)]+[(-13)+13]
=0+[(-6)+6]+0
=0+0+0=0
-6+12-(-6)+(-13)+(-12)+13=-6+12+6+(-13)+(-12)=(-6+6)+(-12+12)+(-13)=0+0+(-13+13)=0+0+0=0
tính A= 5/13+5/12+5/11+5/10 trên 6/13+6/12+6/11+6/10 - 3/4
1.tính nhanh (nếu có thể)
a)29.(19-13)-19.(29-13)
b)31.(-18)+31.(-81)-31
c)(7.3-3):(-6)
d)72:[(-6).2+4)]
2 tính nhanh (nếu có thể)
a)(-12).47+(-12).52+(-12)
b)13.(23+22)-3.(17+28)
c)18-10:(-2)-7
d)99:[(-7).2+5)
Tính ( - 9).( - 12) - ( - 13).6
A. 186
B. 164
C. 30
D. 168
bài 2: tính nhanh :
a) 3/8 + 7/12 + 10/16 + 10/24 b) 4/6 + 7/13 + 17/9 + 19/13 + 1/9 + 14/6
c) 1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42 + 1/56
Tim B=81.((12-12/7-12/289-12/85)/(4-4/7-4/289-4/85))/((5+5/13+5/169+5/91)/(6+6/13+6/169+6/91)).158158158/711711711
Tim B=81.((12-12/7-12/289-12/85)/(4-4/7-4/289-4/85))/((5+5/13+5/169+5/91)/(6+6/13+6/169+6/91)).158158158/711711711
Thực hiện phép tính:
\(B=81.\left[\frac{12-\frac{12}{7}-\frac{12}{289}-\frac{12}{85}}{4-\frac{4}{7}-\frac{4}{289}-\frac{4}{85}}:\frac{5+\frac{5}{13}+\frac{5}{169}+\frac{5}{91}}{6+\frac{6}{13}+\frac{6}{169}+\frac{6}{91}}\right].\frac{158158158}{711711711}\)
a) 21/47 + 9/45 +26/47 + 4/5
= (21/47 + 26/47) + (9/45 + 4/5)
=1+1 = 2
b) 15/12 + 5/13 - 3/12 - 18/13
= (15/12 - 3/12) + (18/13 - 5/13)
=1+1 = 2
c) 13/25 + 6/41 - 38/25 + 35/41 - 1/2
= (38/25 - 13/25) + (35/41 + 6/41) + 1/2
= 1+1 + 1/2 = 5/2
d) 27/23 + 5/21 - 4/23 + 6/21 + 1/2
= (27/23 - 4/23) + (6/21 - 5/21) + 1/2
= ..........................
Đúng không? Phần sau mình tính sao ra kết quả lạ lắm, tính giúp mình.
tinh B
B=81.[12-12/7-12/289-12/85/4-4/7-4/289-4/85:5+5/13=5/169+5/91/6+6/13+6/169+6/91].158158158/711711711
