Find the value of a and b if
x- 1
and
x -2
are factors of
x3-ax+b.
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Find the value of a and b if
x- 1
and
x -2
are factors of
x3-ax+b.
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then x-1=0 and x-2=0
x=1 and x=2
now putting x=1 and x=2 in the eqn and solving simultaneously we get
1-a+b=0 -------(1)
8-2a+b=0-----(2)
we can write the eqns as
-a+b = -1
-2a+b = -8
changing the sign of eqn (2) we get
-a+b = -1
2a-b = 8
---------------
a = 7
now putting the value of a in eqn (1) we get
-7+b = -1
b = -1+7
b = 6