Tính : 1/x^2 =1/6^2+1/8^2
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Bài 2:
a: 2/6x5/3=10/18=5/9
b: 11/9x5/10=55/90=11/18
c: 3/9x6/8=1/3x3/4=1/4
d: 4/9x12/16=48/144=1/3
e: 25/15x6/7=5/3x6/7=30/21=10/7
f: 6/10x15/20=90/200=9/20
Bài 1
4/5 x 6/7= 24/35
2/9 x 1/2= 2/18= 1/9
1/2 x 8/3= 8/6= 4/3
7/9 x 6/5= 42/45= 14/15
8/7 x 5/9= 40/63
10/11 x 22/15= 220/165= 4/3
Bài 2
2/6 x 5/3= 1/3 x 5/3=5/9
11/9 x 5/10= 11/9 x 1/2= 11/18
3/9 x 6/8= 1/3 x 3/4 =3/12= 1/4
4/9 x 12/16= 4/9 x 3/4= 12/36= 1/3
25/15 x 6/7= 5/3 x 6/7= 30/21= 10/7
6/10 x 15/20= 3/5 x 3/4= 9/20
1) 1/3 x 1/2 x 3/7 = 3/42 = 1/14
2) 5/4 x 1/3 +1/7 = 5/12 + 1/7 = 35/84 + 12/84 = 47/84
3) 8 x ( 8/9 - 2/3 ) = 8 x 2/9 = 16/9
4) 5/6 x 48/20 x 1/2 = 240/240 = 1
5) ( 2/5 + 3/4 ) + 8 = 23/20 + 8 = 23//20 + 160/20 = 183/20
6) 10 x ( 1/2 - 1/5 ) = 10 x 3/10 = 10/1 x 3/10 = 30/10 = 3
Bài 1 :
S = \(\frac{6}{2.5}+\frac{6}{5.8}+...+\frac{6}{29.32}\)
= 2 . \(\left(\frac{3}{2.5}+\frac{3}{5.8}+...+\frac{3}{29.32}\right)\)
= 2 . \(\left(\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+...+\frac{1}{29}-\frac{1}{32}\right)\)
= 2 . \(\left(\frac{1}{2}-\frac{1}{32}\right)\)= ....
\(\dfrac{7}{8}\) \(\times\) \(\dfrac{1}{6}\) + \(\dfrac{7}{8}\) \(\times\) \(\dfrac{2}{6}\) + \(\dfrac{7}{8}\) \(\times\) \(\dfrac{1}{2}\)
= \(\dfrac{7}{8}\) \(\times\) ( \(\dfrac{1}{6}\) + \(\dfrac{2}{6}\) + \(\dfrac{1}{2}\) )
= \(\dfrac{7}{8}\) \(\times\) ( \(\dfrac{3}{6}\) + \(\dfrac{1}{2}\))
= \(\dfrac{7}{8}\) \(\times\) ( \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\))
= \(\dfrac{7}{8}\) \(\times\) 1
= \(\dfrac{7}{8}\)
25 \(\times\) 5 \(\times\) 4 \(\times\)2 - 176
= (25 \(\times\) 4 ) \(\times\) ( 5 \(\times\) 2) - 176
= 100 \(\times\) 10 - 176
= 1000 - 176
= 824
\(\dfrac{7}{8}\times\dfrac{1}{6}+\dfrac{7}{8}\times\dfrac{2}{6}+\dfrac{7}{8}\times\dfrac{1}{2}\)
\(=\dfrac{7}{8}\times\left(\dfrac{1}{6}+\dfrac{2}{6}+\dfrac{1}{2}\right)\)
\(=\dfrac{7}{8}\times1\)
\(=\dfrac{7}{8}\)
__________________________
\(25\times5\times4\times2-176\)
\(=\left(25\times4\right)\times\left(4\times2\right)-176\)
\(=1000-176\)
\(=824\)
Chúc bạn học tốt
a,C1
(5/6 + 5/8) x 2/3
= 35/24 x 2/3
=35/36
C2
(5/6 + 5/8) x 2/3
= 5/6x2/3 + 5/8x2/3
= 10/18 + 10/24
= 35/36
b,C1
7/5 x 3/4 - 1/2 x 3/4
= 21/20 - 3/8
= 27/40
C2
7/5 x 3/4 - 1/2 x 3/4
=3/4 x (7/5-1/2)
=3/4x9/10
=27/40
a, 5/6 x (1/8x2/3)
=5/6 x 1/12
=5/72
b,(7/5 - 1/2) x 3/4
=0,9 x 3/4
=3,06
c,(5/6+5/8) x 2/3
=70/48 x 2/3
=35/36
a, 5/6 x (1/8x2/3)
=5/6 x 1/12
=5/72
b,(7/5 - 1/2) x 3/4
=0,9 x 3/4
=3,06
c,(5/6+5/8) x 2/3
=70/48 x 2/3
=35/36
\(\dfrac{1}{1\times2}+\dfrac{1}{2\times3}+\dfrac{1}{3\times4}+\dfrac{1}{4\times5}+\dfrac{1}{5\times6}+\dfrac{1}{6\times7}+\dfrac{1}{7\times8}\)
\(=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{6}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{8}\)
\(=1-\dfrac{1}{8}=\dfrac{7}{8}\)