Mathematics
If (x - 2) is a factor of the expression 2x3 + ax2 + bx - 14 and when the expression is divided by (x - 3), it leaves a remainder 52, find the values of a and b.
Factorisation
3 Likes
Answer
Let f(x) = 2x3 + ax2 + bx - 14
Since, (x − 2) is a factor of f(x) then f(2) = 0.
⇒ 2(2)3 + a(2)2 + b(2) - 14 = 0
⇒ 2(8) + 4a + 2b - 14 = 0
⇒ 16 + 4a + 2b - 14 = 0
⇒ 4a + 2b + 2 = 0
⇒ 4a + 2b = -2
⇒ 2(2a + b) = -2
⇒ 2a + b =
⇒ 2a + b = -1 ….(1)
On dividing f(x) by (x − 3), the remainder is 52,
By remainder theorem,
⇒ f(3) = 52
⇒ 2(3)3 + a(3)2 + b(3) - 14 = 52
⇒ 2(27) + 9a + 3b - 14 = 52
⇒ 54 + 9a + 3b - 14 = 52
⇒ 9a + 3b + 40 = 52
⇒ 9a + 3b = 52 - 40
⇒ 9a + 3b = 12
⇒ 3(3a + b) = 12
⇒ 3a + b =
⇒ 3a + b = 4 ….(2)
Subtracting equation (1) from (2), we get :
⇒ 3a + b - (2a + b) = 4 - (-1)
⇒ a = 4 + 1
⇒ a = 5.
Substituting a = 5 in equation (1), we get :
⇒ 2(5) + b = -1
⇒ 10 + b = -1
⇒ b = -1 - 10
⇒ b = -11.
Hence, the value of a = 5 and b = -11.
Answered By
3 Likes
Related Questions
If (x - 2) is a factor of (x3 + 2x2 - kx + 10), find the value of k. Hence, determine whether (x + 5) is also a factor of the given expression.
Using the remainder and factor theorems, factorize the polynomial.
x3 + 10x2 - 37x + 26
The polynomial 3x3 + 8x2 - 15x + k has (x - 1) as a factor. Find the value of k. Hence factorize the resulting polynomial completely.
It is given that (x − 2) is a factor of polynomial 2x3 − 7x2 + kx − 2.
Find:
(a) the value of ‘k’.
(b) hence, factorise the resulting polynomial completely.