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Find A, B and C if .
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(1) Consider both sides at x--> 1.
Left side tends to infinity as .
Right side tends to infinity as = = .
From it, we conclude that A = 1.
(2) Consider both sides at x--> 2.
Left side tends to infinity as .
Right side tends to infinity as = = .
From it, we conclude that B = -2.
(3) Consider both sides at x--> 3.
Left side tends to infinity as .
Right side tends to infinity as = = .
From it, we conclude that C = 3.
ANSWER. A = 1, B = -2, C = 3.
Solved.
It is the way to solve the problem practically "on fingers",
without reducing to the system of 3 equations in 3 unknowns.