tính hợp lí A= (1+1/1+2)(1+1/1+2+3)(1+1/1+2+3+4)...(1+1/1+2+3+...+997)
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Tính hợp lí:
\(\left(1+\frac{1}{1+2}\right)\cdot\left(1+\frac{1}{1+2+3}\right)\cdot...\cdot\left(1+\frac{1}{1+2+3+...+997}\right)\)
12 tháng 5 2017 lúc 18:06
Tính giá trị biểu thức sau một cách hợp lí:
\(A=\left(1+\frac{1}{1+2}\right)\times\left(1+\frac{1}{1+2+3}\right)\times...\times\left(1+\frac{1}{1+2+...+997}\right)\)
tính hợp lí ( nếu có):
a) (1/2-1). ( 1/3-1)....(1/2016-1)
b) (2/1/3+3/1/2):(-4/1/6+3/1/7)+7/1/2
14 tháng 9 2021 lúc 10:40
Tính hợp lí:
\(1-\dfrac{1}{2}+2-\dfrac{2}{3}+3-\dfrac{3}{4}-4-\dfrac{1}{3}-2-\dfrac{1}{2}-1\)
\(1-\dfrac{1}{2}+2-\dfrac{2}{3}+3-\dfrac{3}{4}-4-\dfrac{1}{3}-2-\dfrac{1}{2}-1=\left(1-1\right)-\left(\dfrac{1}{2}+\dfrac{1}{2}\right)+\left(3-4\right)-\left(\dfrac{1}{3}+\dfrac{2}{3}\right)+\left(2-2\right)-\dfrac{3}{4}=0-1-1-1+0-\dfrac{3}{4}=-3-\dfrac{3}{4}=-\dfrac{15}{4}\)
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\(1-\dfrac{1}{2}+2-\dfrac{2}{3}+3-\dfrac{3}{4}-4-\dfrac{1}{3}-2-\dfrac{1}{2}-1\)
\(=\left(1-1\right)+\left(2-2\right)+\left(3-4\right)+\left(-\dfrac{1}{2}-\dfrac{1}{2}\right)+\left(-\dfrac{2}{3}-\dfrac{1}{3}\right)-\dfrac{3}{4}\)
\(=0+0+\left(-1\right)+\left(-1\right)+\left(-1\right)-\dfrac{3}{4}\)
\(=-3-\dfrac{3}{4}\)
\(=\dfrac{-12}{4}-\dfrac{3}{4}\)
\(=\dfrac{-15}{4}\)
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Thực hiện phép tính hợp lí nhất
1 +1/2 (1+2) +1/3 ( 1+ 2 +3 ) + 1/4 (1+2+3+4) + ....+ 1/20 (1+2+3+....+20)
=1+1/2.(3.2/2)+1/3.(4.3/2)+1/4.(5.4/2)+...+1/20.(21.20/2)
=1+3/2+2+5/2+...+21/2 ( rút gọn)
=2/2+3/2+4/2+5/2+...+21/2
=(2+3+4+5+...+21)/2=(20.23)/2.2=(20.23)/4
=23.5=115
Ko bt mk lm dung ko nx?
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1. Tính hợp lí
a, A=11/125-17/18-5/7+4/9+17/14
b, B=1-1/2+2-2/3+3-3/4+4-1/4-3-1/3-2-1/2-1
c, C=1/100-1/100.99-1/99.98.......-1/3.2-1/2.1
khó nhìn lắm bn ak
sao pn ko cho
\(\frac{11}{125}-\frac{17}{18}-\frac{5}{8}+\frac{4}{9}+\frac{17}{14}.\)
thì có phải dễ nhìn hơn ko
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a, \(A=\frac{11}{125}-\frac{17}{18}-\frac{5}{7}+\frac{4}{9}+\frac{17}{14}\)
\(=\frac{11}{125}+\left(\frac{-17}{18}+\frac{4}{9}\right)+\left(\frac{-5}{7}+\frac{17}{14}\right)\)
\(=\frac{11}{125}+\frac{-1}{2}+\frac{1}{2}\)
\(=\frac{11}{125}\)
b, \(B=1-\frac{1}{2}+2-\frac{2}{3}+3-\frac{3}{4}+4-\frac{1}{4}-3-\frac{1}{3}-2-\frac{1}{2}-1\)
\(=\left(1+2+3+4-3-2-1\right)-\left(\frac{1}{2}+\frac{2}{3}+\frac{3}{4}+\frac{1}{4}+\frac{1}{3}+\frac{1}{2}\right)\)
\(=4-3=1\)
c, \(C=\frac{1}{100}-\frac{1}{100.99}-\frac{1}{99.98}-...-\frac{1}{3.2}-\frac{1}{2.1}\)
\(=\frac{1}{100}-\left(\frac{1}{100.99}+\frac{1}{99.98}+...+\frac{1}{3.2}+\frac{1}{2.1}\right)\)
\(=\frac{1}{100}-\left(\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{98.99}+\frac{1}{99.100}\right)\)
\(=\frac{1}{100}-\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{98}-\frac{1}{99}+\frac{1}{99}-\frac{1}{100}\right)\)
\(=\frac{1}{100}-\left(1-\frac{1}{100}\right)=\frac{1}{100}-\frac{99}{100}=\frac{-49}{50}\)
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Thực hiện phép tính 1 cách hợp lí:
a, 11/125-17/18-5/7+4/9+17/14
b,1-1/2+2-2/3+3-3/4+4-1/4-3-1/3-2-1/2-1
Tính A=\(\left(1+\frac{1}{1+2}\right).\left(1+\frac{1}{1+2+3}\right).\left(1+\frac{1}{1+2+3+4}\right)......\)\(+\left(1+\frac{1}{1+2+3+....997+998}\right)\)
Tính hợp lí:
7[2/1/3+3/1/2]:[)-4/1/6+3/1/7]+7/1/2
