JEE Advanced Mathematics question
Let be divisible by 4, where are digits. The largest possible number of values of is .
Answer: 45000
Solution
Work modulo 4 (each ):
3 ≡ -1, 5 ≡ 1, 7 ≡ -1, 9 ≡ 1 ±od 4,
so
E ≡ + (- + 1 + (- + 1 ±od 4.
Let ; iff have opposite parity.
- : , which is odd
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