If has (x-2) as a factor and leaves a remainder 3 when divided by (x-3), find the values of a and b.

Let f(x) = (x3 + ax2 + bx + 6)


By using remainder theorem,


If we divide f(x) by (x – 3) then it will leave a remainder as f(3)


So,


f(3) = 32 + a × 32 + b × 3 + 6 = 3


27 + 9a + 3b + 6 = 3


9a + 3b + 33 = 3


9a + 3b = 3 – 33


9a + 3b = -30


3a + b = -10 (i)


It is also given that,


(x – 2) is a factor of f(x)


Therefore,


By using factor theorem, we get


(x – a) is the factor of f(x) if f(a) = 0and also f(2) = 0


Now,


f(2) = 23 + a × 22 + b × 2 + 6 = 0


8 + 4a + 2b + 6 = 0


4a + 2b = -14


2a + b = -7 (ii)


Now by subtracting (ii) from (i), we get


a = -3


Putting the value of a in (i), we get


3(-3) + b = -10


-9 + b = -10


b = -10 + 9


b = -1


Therefore,


b = -1 and a = -3


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