Tag: remainder and factor theorems

Questions Related to remainder and factor theorems

$p(x)=(x^2-10x-24)$ , when divided by $x+2$ and $x\neq -2$ gives the quotient $Q$. Find $Q$.

  1. $x -22$

  2. $x-12$

  3. $x+12$

  4. $x+22$


Correct Option: B
Explanation:
 Quotient  $x - 12$
 $x+2$   $x^2-10x-24$  $x^2+2x$$- $   $-$
         $ -12x-24$        $ -12x-24$       $+$        $+$------------------------------                 $ 0$

Using division algorithm method we get the value of $Q = x - 12$.

When $(x^3-2x^2+px-q)$ is divided by $(x^2-2x-3)$, the remainder is $(x-6)$. The values of $p$ and $q$ respectively are ____. 

  1. $-2, 7$

  2. $2, -6$

  3. $-2, 6$

  4. $2, 6$


Correct Option: C
Explanation:

$x^2-2x-3=(x+1)(x-3)$

$x^3-2x^2+px-q-(x-6)=0$ at $x=-1$ and $x=3$.         ($\because (x-6)$ is the remainder)
put $x=-1$,
$-1-2-p-q+1+6=0\ \Rightarrow p+q=4\dots eqn (1)$
Now, put $x=3$
$27-18+3p-q-3+6=0\ \Rightarrow 3p-q=-12\dots eqn (2)$
Add equation 1 and 2, we get
$4p=-8\Rightarrow p=-2$
 and $q=4-p=6$

When a polynomial $P(x)$ is divided by $x, (x - 2)$ and $(x - 3)$, remainders are $1$, $3$ and $2$ respectively. the same polynomial is divided by $x(x - 2)(x - 3)$, the remainder is $ax^2 + bx + c$, then the value of $c$ is

  1. $-3$

  2. $-2$

  3. $6$

  4. $1$


Correct Option: D
Explanation:

According to factor theorem

$p(x)=xq(x)+1$
$P(x)=(x-2)q'(x)+3$
$P(x)=(x-3)q''(x)+2$
So, At $x=0 , P(0)=1$
At $x=2 , P(2)=3$
At $x=3 , P(3)=2$
Now when the polynomial $P(x)$ is divided by $(x-2)(x-3)x$ the remainder must have the degree less than $3$ . that is the remainder will be of the form $ax^2+bx+c$
$\implies P(x)=x(x-2)(x-3)q''''(x)+ax^2+bx+c$
So, $P(0) =1=a(0)^2+b(0)+c\implies c=1$

The quotient and remainder when $x^{2002}$ $- 2001$ is divided by $x^{91}$ are 

  1. $x^{91 \times 22}, 2001$

  2. $x^{91}, 2001$

  3. $x^{91\times 21}, -2001$

  4. $x^9, -2001$


Correct Option: C
Explanation:

$2002 = 91 \times 22$

$\therefore x^{2002} = x^{91 \times 22}$
$\therefore$ $x^{2002} - 2001$ $=$ $x^{91} \times (x^{91 \times 21}) - 2001$

When $x^{91} \times (x^{91 \times 21}) - 2001$ is divided by $x^{91}$, then
Quotient $= x^{91 \times 21}$ 
And 
Remainder $= -2001$

Which of the following given options is/ are correct?
If $p(x)=q(x)g(x)+r(x)$ (By Division Algorithm) where p(x), g(x) are any two polynomials with $g(x)\neq 0$, then

  1. $r(x)=0$ always

  2. degree of r(x)< degree of g(x) always

  3. either $r(x)=0$ or degree of r(x)< degree of g(x)

  4. $r(x)=g(x)$


Correct Option: C
Explanation:

(a) If p(x) is not divisible by g(x), then $r(x)\neq 0 \therefore$ (a) is not true
(b) If p(x) is divisible by g(x), the $r(x)=0$ for all x i.e., r(x) is zero polynomial whose degree is not defined.
$\therefore $(b) is not true
(c) is clearly true [$\because$ division algorithm rule]
Since degree of $r(x)<$ degree of g(x) or $r(x)=0$, but $g(x)\neq 0$.
(d) $\therefore r(x)=g(x)$ is not true.

A polynomial $f(x)$ with rational coefficient leaves reminder $15$, when divided by $(x-3)$ and remainder $2x+1$, when divided by $(x-1)^{2}$. If $p$ is coefficient of $x$ of its remainder which will come out if $f(x)$ is divided by $(x-3)(x-1)^{2}$ then find $p$.

  1. $-2$

  2. $-1$

  3. $1$

  4. $6$


Correct Option: A