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D( A )
A = 0
400/A <= 0
200/A <= 0
A = 0
A = 0
400/A <= 0
400/A <= 0
400*A^-1 <= 0
400*A^-1 <= 0 // : 400
A^-1 <= 0/400
A^-1 <= 0
1/(A^1) <= 0
A <> 0
1/(A^1) <= 0 // * A^2
(A^2)/(A^1) <= 0
A^1 <= 0
A <= 0
A in (-oo:0)
200/A <= 0
200/A <= 0
200*A^-1 <= 0
200*A^-1 <= 0 // : 200
A^-1 <= 0/200
A^-1 <= 0
1/(A^1) <= 0
A <> 0
1/(A^1) <= 0 // * A^2
(A^2)/(A^1) <= 0
A^1 <= 0
A <= 0
A in (-oo:0)
A in (0:+oo)
4*ln(400/A) = 3*ln(200/A) // - 3*ln(200/A)
4*ln(400/A)-(3*ln(200/A)) = 0
4*ln(400/A)-3*ln(200/A) = 0
ln(1*(400/A)^4)-3*ln(200/A) = 0
ln((1*(400/A)^4)/((200/A)^3)) = 0
ln(((400/A)^4)/((200/A)^3)) = 0
ln(((400/A)^4)/((200/A)^3)) = ln(e^0)
((400/A)^4)/((200/A)^3) = e^0
((400/A)^4)/((200/A)^3)-e^0 = 0
3200*A^-1 = 1 // : 3200
A^-1 = 1/3200
-1 < 0
1/(A^1) = 1/3200 // * A^1
1 = 1/3200*A^1 // : 1/3200
3200 = A^1
A = 3200
A = 3200
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