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a) = 17/19 - 17/19 + 27/35 + 35/35 = 0 + 62/35
b) = 1/3 x 4/5 + 1/3 x6/5 + 1/3 x 2 = 1/3(4/5 + 6/5 + 2) = 1/3 x 4 = = 4/3
c) 4/7 x 2/9 + 4/7 x 7/9 + 2/3 = 4/7 x (2/9 + 7/9) + 2/3 = 4/7 x 1 + 2/3 = 26/21
A) 17/19 - 17/19 + 27/35 + 35/35 = 0 + 62/35
B) 1/3 x 4/5 + 1/3 x 6/5 + 1/3 x 2 = 1/3 x(4/5 + 6/5 x 2 ) = 1/3 x 4 = 4/3
c) TƯƠNG TỰ CÂU A VÀ B
* HOKTOT*
NHA
a,\(\frac{2}{5}+\frac{3}{4}=\frac{8+15}{20}=\frac{23}{20}\)
\(\frac{7}{12}-\frac{2}{7}+\frac{1}{12}=(\frac{7}{12}+\frac{1}{12})-\frac{2}{7}\)
\(=\frac{2}{3}-\frac{2}{7}=\frac{14-6}{21}=\frac{8}{21}\)
\(\frac{12}{17}-\frac{5}{17}-\frac{4}{17}=\frac{7}{17}-\frac{4}{17}=\frac{3}{17}\)
b,\(675,39+342,14=1017,53\)
\(563,87+403,13-328,35=638,65\)
2/5+3/4=23/20
7/12-2/7+1/12=8/21
12/17-5/17-4/173/17
675,39+342,14=1017,53
563,87+403,13-328,35=638,65
\(\frac{7}{9}.\frac{8}{17}+\frac{15}{9}-\frac{7}{9}.\frac{6}{12}=\frac{56}{153}+\frac{15}{9}-\frac{7}{18}=\frac{503}{306}\)
ủng hộ nha
1+1+2+2+3+3+4+4+5+5+6+6+7+7+8+9+8+9+10+12+13+14+15+16+17+18+19+20+30+1000000=10000274
5/7-4/9=17/63
3/8+9/5=87/40
1-5/9=4/9
7/12-2/7+1/12=8/21
12/17-5/17-4/17=3/17
a)=(3/8+10/16)+(7/12+10/24)
=1+1=2
c)=(4/6+14/6)+(7/13+19/13)+(17/9+1/9)
=3+2+2=7
a) Cách 1 : Cách 2
1 + 3 +5 + 7 + 9 + 11 + 13 + 15 + 17 + 19 1 + 3 +5 + 7 + 9 + 11 + 13 + 15 + 17 + 19
=(1 + 19) + (3 + 17) +.... + (9 + 11) Áp dụng công thức tính dãy số ta có :
= 20 + 20 + ... + 20 \(\frac{\left[\left(19-1\right):2+1\right].\left(19+1\right)}{2}=\frac{10.20}{2}=10.10=100\)
= 20 x 5 = 100
b) giống bài a nhưng cách 1 làm dài lắm , mình sẽ làm cách 2
áp dụng công thức tính dãy số ta có:
\(\frac{\left[\left(200-4\right):4+1\right].\left(200+4\right)}{2}=\frac{50.204}{2}=50.102=5100\)
a \(\dfrac{5}{12}\times\dfrac{4}{9}\) + \(\dfrac{4}{9}\times\dfrac{7}{12}\)
= \(\dfrac{4}{9}\times\left(\dfrac{5}{12}+\dfrac{7}{12}\right)\)
= \(\dfrac{4}{9}\times\dfrac{12}{12}\)
= \(\dfrac{4}{9}\)
b(\(\dfrac{13}{21}\times\dfrac{7}{8}-\dfrac{12}{21}\times\dfrac{7}{8}\)) x 12
(\(\dfrac{7}{8}\times\left(\dfrac{13}{21}-\dfrac{12}{21}\right)\))x 12
\(\dfrac{7}{8}\times\dfrac{1}{21}\) x 12
\(\dfrac{139}{14}\)
\(\dfrac{7}{11}+\dfrac{3}{4}+\dfrac{4}{11}+\dfrac{8}{17}+\dfrac{1}{4}+\dfrac{18}{34}\)
=\(\left(\dfrac{7}{11}+\dfrac{4}{11}\right)+\left(\dfrac{3}{4}+\dfrac{1}{4}\right)\) + \(\dfrac{18}{34}\)
=1 + 1 + \(\dfrac{18}{34}\)
=\(\dfrac{34}{17}\)
A ) 2/17 + 30/46 + 15/17 + 4/49 + 8/23=102/49
B ) 5/8 x ( 19/31 x 8/5 )=19/31
C ) 7/9 x 8/15 x 9/7 x 15/4=2
D ) 11/12 x 24/7 x 21/22=3
nhìu quá nên mk chỉ cho kết quả thôi nha ^-^!!!
A,17/12+9/7-2/7+7/12=(17/12+7/12)+(9/7-2/7)=24/12+7/7=2+1=3
B,9/8-(17/7-3/7)+7/8=(9/8+7/8)-14/7=16/8-14/7=2-2=0
Nhớ k nha
a, 17/12+9/7-2/7+7/12
=(17/12+7/12)+(9/7-2/7)
=24/12+7/7
=2+1
=3
b, 9/8-(17/7-3/7)+7/8
=9/8-14/7+7/8
=(9/8+7/8)-14/7
=16/8-14/7
=2-2
=0