> JCD最大公约数
{a∣m=0b∣m=0 \begin{cases} a|m=0 \\ b|m=0 \end{cases} {a∣m=0b∣m=0
所以
gcd(a,b)∣m==0gcd(a,b)|m==0gcd(a,b)∣m==0
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> LCM最小公倍数
{d∣a=0d∣b=0 \begin{cases} d|a=0 \\ d|b=0 \end{cases} {d∣a=0d∣b=0
所以
d∣lcm(a,b)==0d|lcm(a,b)==0d∣lcm(a,b)==0
lcm(m∗a,m∗b)==m∗lcm(a,b)lcm(m*a,m*b)==m*lcm(a,b)lcm(m∗a,m∗b)==m∗lcm(a,b)
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> so
gcl(a,b)∗lcm(a∗b)=∣a∗b∣gcl(a,b)*lcm(a*b)=|a*b|gcl(a,b)∗lcm(a∗b)=∣a∗b∣
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> ERATOSHENES筛法