Jawabanmu

2014-03-31T21:04:36+07:00
A + B = -b/a
         = 4/ (p-2)

A × B = c/a
         = (p+2)/(p-2)

AB² + BA² = -20
ABB + BAA = -20
AB ( A + B ) = -20
( p+2 ) (  4  ) = -20
( p-2 )  ( p-2)

4p + 8 = -20 ( p² - 4p + 4)
-20p² + 80p - 80 - 4p - 8 = 0 
-20p² + 76p - 72 = 0 ( sederhanakan dengan membagi 4)

-5p² + 19p - 18 = 0
(-5p + 9 ) ( p - 2) =  0
p = 9/-5 atau p = 2