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(15x1-15) x) (10+1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20)
= (15-15) x (10+1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20)
= 0 x (10+1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20)
= 0
= (15 - 15)\(\times\)(10 +1 +2 +3 +4 +5 +6 +7 +8 +9 +10 +11 +12 +13 +14 +15 +16 +17 +18 +19 +20)
= 0\(\times\)(10 +1 +2 +3 +4 +5 +6 +7 +8 +9 +10 +11 +12 +13 +14 +15 +16 +17 +18 +19 +20)
= 0
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a=3/4*7/6=1/2+1/3=5/6
b=5/3*9/15=1-1/5=4/5
c=1/4*1/5=1/20:1/3=3/20
d=7/9:14/15=5/6*1/2=5/12
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Bài 1
a 2/5+3/6=12/30+15/30=27/30=9/10 .
b 5/9-1/6=30/54-9/54=21/54=7/18
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a) 2/9 : 2/3 x 1/2
= 2/9 x 3/2 x 1/2
= 6/18 x 1/2
= 6/36
b) 2 + 1/4 x 4/3
= 2 + 4/7
= 2/1(7) + 4/7
= 14/7 + 4/7
= 18/7
c) 3 x 1/2 x 1/4
= 3/1 x 1/2 x 1/4
= 3/2 x 1/4
= 3/8
#Hok_tốt
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\(\frac{1}{2}\)- \(\frac{1}{3}\)x \(\frac{1}{4}\)
= \(\frac{1}{2}\)- \(\frac{1}{12}\)
= \(\frac{6}{12}\)- \(\frac{1}{12}\)
= \(\frac{5}{12}\)
tk nhé
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\(\dfrac{7}{3}\times\dfrac{1}{2}+\dfrac{1}{7}=\dfrac{7}{6}+\dfrac{1}{7}=\dfrac{49}{42}+\dfrac{6}{42}=\dfrac{55}{42}\)