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c b [AHSME 1988]( )
.(x + 2)(x + b) = x2 + cx + 6
.c b

. x2 = −b x1 = −2

. x1 + x2 = −c .b = 3 2b = 6 . x1x2 = 6

.c = 5 .−2 − 3 = −c

.b a ba [AHSME 1988]( )

.ax 3 + bx2 + 1 x2 −x −1

( )ax 3 + bx2 + 1 = (ax + a + b) x2 − x − 1 + (2a + b)x + (a + b + 1)

.(2a + b)x + (a + b + 1)
. x2 −x −1

(2a + b)x + (a + b + 1) = 0

. 2a + b = 0 a +b +1 = 0

.b = −2 a = 1

) f (x) [AMC12B 2003]( )

. f (12) − f (2) . f (6) − f (2) = 12 (

. f (x) = ax + b

f (6) − f (2) = (6a + b) − (2a + b) = 4a