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Bài 1 :
\(-8=\frac{-8}{1}=\frac{-16}{2}=\frac{-24}{3}=\frac{-32}{4}=\frac{-40}{5}\)
\(-2=\frac{-2}{1}=\frac{-4}{2}=\frac{-6}{3}=\frac{-8}{4}=\frac{-10}{5}\)
\(3=\frac{3}{1}=\frac{6}{2}=\frac{9}{3}=\frac{12}{4}=\frac{15}{5}\)
Bài 2 :
a) Để A là phân số thì :
\(n-6\ne0\Rightarrow n\ne6\)
b)\(A=\frac{4}{0-6}=\frac{4}{-6}\)
\(A=\frac{4}{7-6}=4\)
\(A=\frac{4}{-12-6}=\frac{-2}{9}\)
Bài 3 : [ Tương tự bài 2 ]
Bài 4 : [ Suy nghĩ thì ra ]
[ Hoq chắc - có gì sai thông cảm ]
a) = ( 9/10 - 4/5) + ( 3/4 + 1/2)
= ( 9/10 - 8/10) + ( 3/4 + 2/4)
= 1/10 + 5/4
= 2/20 + 25/20 = 27/20
b) = (4/5 + 4/15) + (5/6 - 1/2)
= (12/15 - 4/15) + (5/6 - 3/6)
= 8/15 + 2/6
= 16/30 + 10/30
= 26/30 = 13/15
c) = 55 - 39 - 1 + 60 /75 = 75/75 = 1
d) = 47 + 35 - 36 + 15/42 = 61/42
\(a) {4\over12}={4.5\over12.5}={20\over60}\)
\({1\over5}={1.12\over5.12}={12\over60}\)
\({-4\over15}={-4.4\over15.5}={-16\over60}\)
b)\({-7\over10}={-7.3\over10.3}={-21\over20}\)
\({1\over2}={1.15\over2.15}={15\over30}\)
\({-4\over15}={-4.2\over15.2}={-8\over30}\)
c)\({-5\over14}={-5.30\over14.30}={-150\over420}\)
\({3\over20}={3.21\over20.21}={63\over420}\)
\({-4\over21}={-4.20\over21.20}={-80\over420}\)
d)\({4\over18}={4.5\over18.5}={20\over90}\)
\({1\over18}={1.18\over5.18}={18\over90}\)
\({-6\over15}={-6.6\over15.6}={-36\over90}\)
Nói lời giữ lời nha ^_^..........Mệt wá........
a)4/12=1.5/12.5=5/60
1/5=1.12/5.12=5/60
-4/15=-4.4/15.4=-16/60
b)-7/10=-7.3/10.3=-21/30
1/2=1.15/2.15=15/30
-4/15=-4.2/15.2=-8/30
c)-5/14=-5.30/14/30=150/420
3/20=3.21/20.21=63/420
-4/21=-4.20/21.20=-80/420
d)4/18=4.5/18.5=20/90
1/5=1.18/5.18=18/90
-6/15=-6.6/15.6=-36/90
a: \(\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+...+\dfrac{1}{100\cdot101}\)
=1-1/2+1/2-1/3+...+1/100-1/101
=1-1/101=100/101
b: \(A=1+\dfrac{1}{2}+1+\dfrac{1}{6}+1+\dfrac{1}{12}+...+1+\dfrac{1}{10100}\)
\(=100+\left(1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+...+\dfrac{1}{100}-\dfrac{1}{101}\right)\)
\(=101-\dfrac{1}{101}< 101\)
