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x4 - mx2 + 9 = (x2 -1)2
vây m =6 thì x4 -6x2 +9 chia hết cho x2 - 1
( ngâniq106)
\(1^2-2^2+3^2-4^2+...+97^2-98^2+99^2-100^2=\left(1-2\right)\left(1+2\right)+\left(3-4\right)\left(3+4\right)+...+\left(97-98\right)\left(97+98\right)+\left(99-100\right)\left(99+100\right)\)\(=-\left(1+2+3+4+...+97+98+99+100\right)\)
\(=-\left(\frac{101\times100}{2}\right)=-5050\)
Call the smallest digit a => 3-digit number a, 2a, 3a with 3a ≤ 9 => a ≤ 3. Find the number divisible by 18, which is divisible by 9, so (a + 2a + 3a) = 6a is divisible by 9 => a is divisible by 3, so a = 3 => 3 digits are 3, 6, 9
The number to find is even by dividing by 2, so the last digit is 6
=> 396 or 936
Call the smallest digit a => 3-digit number a, 2a, 3a with 3a ≤ 9 => a ≤ 3. Find the number divisible by 18, which is divisible by 9, so (a + 2a + 3a) = 6a is divisible by 9 => a is divisible by 3, so a = 3 => 3 digits are 3, 6, 9
The number to find is even by dividing by 2, so the last digit is 6
=> 396 or 936