Find the values of a and b so that the polynomial is exactly divisible by (x-1) as well as (x-2).
Let f(x) = x3 – 10x2 + ax + b
Now,
By using factor theorem,
(x – 1) and (x - 2) will be the factors of f(x) if f(1) = 0 and f(2) = 0
Hence,
f(1) = 13 – 10 (1)2 + a × 1 + b
0 = 1 – 10 + a + b
a + b = 9 (i)
And,
f(2) = 23 – 10 × 22 + a × 1 + b
0 = 8 – 40 + 2a + b
2a + b = 32 (ii)
Now, subtracting (i) from (ii)
a = 23
Using the value of a in (i), we get
23 + b = 9
b = 9 – 23
b = -14
Hence,
a = 23 and b = -14