The Polynomial f(x) = x 4 -2x 3 +3x 2 -ax + b when divided by (x-1) and (x+1) leaves the remainders 5 and 19 respectively. Find the values of a and b. Hence, find the remainder when f(x) is divided by (x-2).

Question

The Polynomial f(x) = x 4  -2x 3  +3x 2  -ax + b when divided by (x-1) and (x+1) leaves the remainders 5 and 19 respectively. Find the values of a and b. Hence, find the remainder when f(x)  is divided by (x-2).

Philoid · Accepted Answer

Let f(x) = x⁴ – 2x³ + 3x² – ax + b

Now,

f(1) = 1⁴ – 2(1)³ + 3(1)² – a(1) + b

5 = 1 – 2 + 3 – a + b

3 = - a + b (i)

And,

f(-1) = (-1)⁴ – 2(-1)³ + 3(-1)² – a(-1) + b

19 = 1 + 2 + 3 + a + b

13 = a + b (ii)

Now,

Adding (i) and (ii),

8 + 2b = 24

2b = 16

b = 8

Now,

Using the value of b in (i)

3 = - a + 8

a = 5

Hence,

a = 5 and b = 8

Hence,

f(x) = x⁴ – 2(x)³ + 3(x)² – a(x) + b

= x⁴ – 2x³ + 3x² – 5x + 8

f(2) = (2)⁴ – 2(2)³ + 3(2)² – 5(2) + 8

= 16 – 16 + 12 – 10 + 8

= 20 – 10

= 10

Therefore, remainder is 10

The Polynomial f(x) = x4 -2x3 +3x2 -ax + b when divided by (x-1) and (x+1) leaves the remainders 5 and 19 respectively. Find the values of a and b. Hence, find the remainder when f(x) is divided by (x-2).

The Polynomial f(x) = x⁴ -2x³+3x²-ax + b when divided by (x-1) and (x+1) leaves the remainders 5 and 19 respectively. Find the values of a and b. Hence, find the remainder when f(x) is divided by (x-2).