Tính bằng cách thuận tiên nhất: a) 1/2+1/3+1)4+1)2+2)3+3/4. ; b) ( 3/4+5/7+16/64+2/7)-2
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1/2 + 1/3 + 1/4 + 1/5 + 4/5 + 3/4 + 2/3 + 1/2
= (1/2 + 1/2) + (1/3 + 2/3) + (1/4 + 3/4) + (1/5 + 4/5)
= 1 + 1 + 1 + 1
= 4
\(\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+\dfrac{1}{5}+\dfrac{4}{5}+\dfrac{3}{4}+\dfrac{2}{3}+\dfrac{1}{2}\)
\(=\left(\dfrac{1}{2}+\dfrac{1}{2}\right)+\left(\dfrac{1}{3}+\dfrac{2}{3}\right)+\left(\dfrac{1}{4}+\dfrac{3}{4}\right)+\left(\dfrac{1}{5}+\dfrac{4}{5}\right)\)
=1+1+1+1
=4
1/2 x 1/3 + 1/3 x 1/4 + 1/4 x 1/5 + 1/5 x 1/6
= 1/2 - 1/3 + 1/3 - 1/4 + 1/4 - 1/5 + 1/5 - 1/6
= 1/2 - 1/6
= 1/3
Cach 1 \(\frac{3}{4}\times\frac{1}{2}\times2\)
= \(\frac{3}{4}\times\frac{1}{2}\times\frac{2}{1}\)
= \(\frac{3\times1\times2}{4\times2\times1}\)
= \(\frac{6}{8}\)
= \(\frac{3}{4}\)
Cach 2 \(\frac{3}{4}\times\frac{1}{2}\times2\)
= \(\frac{3}{4}\times\frac{1}{2}\times\frac{2}{1}\)
= \(\frac{3\times1\times2}{4\times2\times1}\)
=\(\frac{3}{4}\)
Đoạn này cần gach nhưng ở đây ko có gạch chéo nên bạn cố gắng hiểu nhé!
Chúc bạn học giỏi
Nhớ cho mình 1 k đúng nhé!
3/4 x 1/2 x 2
C1 : = 3/8 x 2
= 6/8
= 3/4
C2 : = 3/4 x 2/2
= 3/4 x 1
= 3/4
\(\frac{1}{7}+\frac{2}{7}+\frac{3}{7}+\frac{4}{7}+\frac{5}{7}+\frac{6}{7}\)
\(=\left(\frac{1}{7}+\frac{6}{7}\right)+\left(\frac{2}{7}+\frac{5}{7}\right)+\left(\frac{3}{7}+\frac{4}{7}\right)\)
\(=1+1+1=3\)
= 3/2 + 2/3 + 2/4 + 2/5
= (6/4 + 2/4) + (2/3 + 2/5)
= 8/4 + 16/ 15
= 46/15
= 1/2 x ( 3/4 + 1/4 )
= 1/2 x 1
= 1/2
Nếu như thấy thuận tiện thì cho mình 1 nhé. Thanks
\(\dfrac{1}{4}+\dfrac{2}{5}+\dfrac{3}{4}+\dfrac{3}{5}\)
\(=\left(\dfrac{1}{4}+\dfrac{3}{4}\right)+\left(\dfrac{2}{5}+\dfrac{3}{5}\right)\)
\(=1+1\)
\(=2\)
#Sahara |
A = \(\dfrac{1}{2}\)+ \(\dfrac{1}{3}\)+ \(\dfrac{1}{4}\)+ \(\dfrac{1}{2}\)+ \(\dfrac{2}{3}\)+ \(\dfrac{3}{4}\)
A = ( \(\dfrac{1}{2}\)+ \(\dfrac{1}{2}\)) + ( \(\dfrac{1}{4}\)+\(\dfrac{3}{4}\)) +( \(\dfrac{1}{3}\)+ \(\dfrac{2}{3}\))
A = 1 + 1 + 1
A = 3
B = ( \(\dfrac{3}{4}\) + \(\dfrac{5}{7}\)+ \(\dfrac{16}{64}\)+ \(\dfrac{2}{7}\)) - 2
B = ( \(\dfrac{3}{4}\)+ \(\dfrac{1}{4}\)) + ( \(\dfrac{5}{7}\)+ \(\dfrac{2}{7}\)) - 2
B = 1 + 1 - 2
B = 2 - 2
B = 0