Class 9 Polynomials Practice Paper – Questions with Solutions

Polynomials

Section A (1 × 6 = 6 marks)

(Multiple Choice Questions)

  1. Which of the following is a polynomial?
     (a) $\dfrac{1}{x} + 3$ \quad (b) $\sqrt{x} + 2$ \quad (c) $4x^2 - 3x + 7$ \quad (d) $x^{-2} + 1$

  2. A polynomial of degree 4 has at most
    (a) 3 terms
    (b) 4 terms
    (c) 5 terms
    (d) 6 terms

  3.  \text{The coefficient of } x^3 \text{ in } 5x^3 - 2x^2 + x - 9 \text{ is}
    (a) 2
    (b) 5
    (c) –2
    (d) 1

  4. Which of the following is a monomial?
     (a) $x^2 + 1$ \quad (b) $3x^2y$ \quad (c) $x - y$ \quad (d) $x^2 + y^2\quad

  5.  \text{The degree of the polynomial } 7x^5 - 4x^2 + 9 \text{ is}

    (a) 2
    (b) 5
    (c) 7
    (d) 9

  6. Which expression is a binomial?
    (a) $x$ \quad (b) $x^2 + 3x + 1$ \quad (c) $2x^3$ \quad (d) $x + 5$\quad


Section B (2 × 4 = 8 marks)

  1. Find the value of k if x+2 is a factor of

4x^3 - 3x^2 + kx - 6

  1. Factorise:

x^3 - 27

  1. Without actually calculating the cubes, find the value of:

(10)^3 + (5)^3 + (-15)^3

  1. Find the remainder when

f(x) = 2x^3 + x^2 - 5x + 7

is divided by .


Section C (3 × 3 = 9 marks)

  1. Using factor theorem, factorise:

 x^2 - 7x + 10

  1. Without actual division, show that

 3x^3 - 5x^2 - 2x + 4

is divisible by x−1.

  1. Using suitable identity, expand:

 \left(\frac{3}{2}x - \frac{1}{3}\right)^2


Section D (5 × 1 = 5 marks)

  1. If

 x^2 + ax + b = (x + 3)(x - 5)

find the values of a and b, and hence factorise:

 x^2 + ax - b


Answer Key

Section A – MCQs

 1.\ (c)\ 4x^2 - 3x + 7

 2.\ (c)\ 5\ terms

 3.\ (b)\ 5

 4.\ (b)\ 3x^2y

 5.\ (b)\ 5

 6.\ (d)\ x + 5


Section B

7. Find the value of k

 Given,\ f(x)=4x^3 - 3x^2 + kx - 6

 Since\ (x+2)\ is\ a\ factor,\ f(-2)=0

 4(-2)^3 - 3(-2)^2 + k(-2) - 6 = 0

 -32 - 12 - 2k - 6 = 0

 -50 - 2k = 0

 k = -25


8. Factorise

x^3 - 27

 x^3 - 27 = (x - 3)(x^2 + 3x + 9)


9. Without calculating cubes

 (10)^3 + (5)^3 + (-15)^3

 a^3 + b^3 + c^3 - 3abc = (a+b+c)(a^2 + b^2 + c^2 - ab - bc - ca)

 Here,\ a+b+c = 10 + 5 - 15 = 0

 \therefore\ value = 0


10. Remainder theorem

 f(x) = 2x^3 + x^2 - 5x + 7

 Remainder = f(1)

 = 2(1)^3 + (1)^2 - 5(1) + 7

 = 2 + 1 - 5 + 7 = 5


Section C

11. Factorise using factor theorem

 x^2 - 7x + 10

 = (x - 5)(x - 2)


12. Prove divisibility

 f(x) = 3x^3 - 5x^2 - 2x + 4

 f(1) = 3 - 5 - 2 + 4 = 0

 \therefore\ (x - 1)\ is\ a\ factor


13. Expand

 \left(\frac{3}{2}x - \frac{1}{3}\right)^2

 = \left(\frac{3}{2}x\right)^2 - 2\left(\frac{3}{2}x\right)\left(\frac{1}{3}\right) + \left(\frac{1}{3}\right)^2

 = \frac{9}{4}x^2 - x + \frac{1}{9}


Section D

14. Find a and b

 x^2 + ax + b = (x + 3)(x - 5)

 = x^2 - 2x - 15

 a = -2,\ b = -15

 x^2 + ax - b = x^2 - 2x + 15

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