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\(a,x+\dfrac{2}{5}=\dfrac{1}{2}\\ x=\dfrac{1}{2}-\dfrac{2}{5}\\ x=\dfrac{1}{10}\\b,x=\dfrac{2}{5}+\dfrac{3}{7}\\ x=\dfrac{29}{35}\\ c,=\dfrac{19}{20}-\dfrac{8}{5}\\ x=\dfrac{-13}{20} \)
a: x+2/5=1/2
=>x=1/2-2/5=5/10-4/10=1/10
b: x-3/7=2/5
=>x=2/5+3/7=14/35+15/35=29/35
c: 19/20-x=8/5
=>x=19/20-8/5=19/20-32/20=-13/20
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\(\frac{12}{3\cdot7}+\frac{12}{7\cdot11}+...+\frac{12}{43\cdot47}=3\left(\frac{4}{3\cdot7}+\frac{4}{7\cdot11}+...+\frac{4}{43\cdot47}\right)=3\left(\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+...+\frac{1}{43}-\frac{1}{47}\right)\)\(=3\left[\left(\frac{1}{3}-\frac{1}{47}\right)+\left(\frac{1}{7}-\frac{1}{7}\right)+...+\left(\frac{1}{43}-\frac{1}{43}\right)\right]=3\left[\left(\frac{47}{141}-\frac{3}{141}\right)+0+...+0\right]=3\cdot\frac{44}{141}=\frac{44}{47}\)
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Mọi người tk mình đi mình đang bị âm nè!!!!!!
Ai tk mình mình tk lại nha !!!
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7365 - 365 x ( 735 - 328 ) : 55
= 7365 - 365 x 407 : 55
= 7365 - 148 555 : 55
= 7365 - 2701
= 4664.
Mongg k~
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hùng có số viên bi là : 18
dũng có số viên bi là : 30
mình chắc 100% luôn
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