Find the number of integer solutions of the above equation.
If the answer can be expressed in the form , enter .
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First notice that 2 1 0 = 2 ⋅ 3 ⋅ 5 ⋅ 7
Now let a = 2 x 1 3 y 1 5 z 1 7 ω 1 , b = 2 x 2 3 y 2 5 z 2 7 ω 2 , c = 2 x 3 3 y 3 5 z 3 7 ω 3 , d = 2 x 4 3 y 4 5 z 4 7 ω 4
So a ⋅ b ⋅ c ⋅ d = 2 x 1 3 y 1 5 z 1 7 ω 1 ⋅ 2 x 2 3 y 2 5 z 2 7 ω 2 ⋅ 2 x 3 3 y 3 5 z 3 7 ω 3 ⋅ 2 x 4 3 y 4 5 z 4 7 ω 4
0 0 0 0 ≤ x 1 + x 2 + x 3 + x 4 ≤ y 1 + y 2 + y 3 + y 4 ≤ z 1 + z 2 + z 3 + z 4 ≤ ω 1 + ω 2 + ω 3 + ω 4 ≤ 1 ≤ 1 ≤ 1 ≤ 1
Each of these equations have 4 positive integer solutions meaning a b c d = 2 1 0 has 4 × 4 × 4 × 4 = 4 4 positive integer solutions.
Now for all integer solutions we must consider negatives. We can arbitrarily assign the signs to any three positive integers and only the last one will determine if the result is positive or negative. We can assign the signs in 2 3 = 8 ways.
So the number of integer solutions is 2 3 ⋅ 4 4 = 2 3 ⋅ 2 8 = 2 1 1 ⟹ 2 n = 2 ⋅ 1 1 = 2 2