The polynomial f(x)=x^4-2x^3+3x^2-9x+3a-7 when divided by x+1 leaves the remainder 20 . Find the value of a. Also find the remainder when p(x) is divided by x+1
Answers
Given polynomial p(x) = x4- 2x3 + 3x2- 9x - 7 + 3b.
When divided by x+1 leaves a remainder 29 i.e.
as per the remainder theorem, p(-1) = 29.
But p(-1) = 1 + 2 + 3 + 9 - 7 + 3b = 29
⇒ 8 + 3b = 29
⇒ 3b = 21
∴ b = 7.
Answer:
p(x) = x4 – 2x3 + 3x2 – ax + 3a – 7
Divisor = x + 1
x + 1 = 0
x = -1
So, substituting the value of x = – 1 in p(x),
we get,
p(-1) = (-1)4 – 2(-1)3 + 3(-1)2 – a(-1) + 3a – 7.
19 = 1 + 2 + 3 + a + 3a – 7
19 = 6 – 7 + 4a
4a – 1 = 19
4a = 20
a = 5
Since, a = 5.
We get the polynomial,
p(x) = x4 – 2x3 + 3x2 – (5)x + 3(5) – 7
p(x) = x4 – 2x3 + 3x2 – 5x + 15 – 7
p(x) = x4 – 2x3 + 3x2 – 5x + 8
As per the question,
When the polynomial obtained is divided by (x + 2),
We get, x + 2 = 0
x = – 2
So, substituting the value of x = – 2 in p(x), we get,
p(-2) = (-2)4 – 2(-2)3 + 3(-2)2 – 5(-2) + 8
⇒ p(-2) = 16 + 16 + 12 + 10 + 8
⇒ p(-2) = 62 Therefore, the remainder = 62.
Answer:
p(x) = x4 – 2x3 + 3x2 – ax + 3a – 7
Divisor = x + 1
x + 1 = 0
x = -1
So, substituting the value of x = – 1 in p(x),
we get,
p(-1) = (-1)4 – 2(-1)3 + 3(-1)2 – a(-1) + 3a – 7.
19 = 1 + 2 + 3 + a + 3a – 7
19 = 6 – 7 + 4a
4a – 1 = 19
4a = 20
a = 5
Since, a = 5.
We get the polynomial,
p(x) = x4 – 2x3 + 3x2 – (5)x + 3(5) – 7
p(x) = x4 – 2x3 + 3x2 – 5x + 15 – 7
p(x) = x4 – 2x3 + 3x2 – 5x + 8
As per the question,
When the polynomial obtained is divided by (x + 2),
We get, x + 2 = 0
x = – 2
So, substituting the value of x = – 2 in p(x), we get,
p(-2) = (-2)4 – 2(-2)3 + 3(-2)2 – 5(-2) + 8
⇒ p(-2) = 16 + 16 + 12 + 10 + 8
⇒ p(-2) = 62 Therefore, the remainder = 62.