Class 10 Maths – Quadratic Equations MCQ

1. The general form of a quadratic equation is:

a) ax^2 + bx + c = 0
b) ax + by + c = 0
c) ax^2 + bx = 0
d) ax^2 + c = 0

Answer:

a) ax^2 + bx + c = 0

Explanation:

A quadratic equation is of the form ax^2 + bx + c = 0, where a, b, and c are constants and a ≠ 0.

2. The roots of the equation x^2 – 6x + 9 = 0 are:

a) 3 and 3
b) 3 and -3
c) -3 and -3
d) 6 and 0

Answer:

a) 3 and 3

Explanation:

The given equation is a perfect square trinomial. It can be written as (x-3)(x-3) = 0. Hence, the roots are 3 and 3.

3. If the quadratic equation px^2 + 6x + r = 0 has equal roots, then:

a) p = r
b) p^2 = 4r
c) p = 3r
d) r^2 = 36p

Answer:

d) r^2 = 36p

Explanation:

For equal roots, discriminant b^2 – 4ac = 0. Plugging in the values, we get 36 – 4pr = 0.

4. The quadratic equation whose roots are 4 and -5 is:

a) x^2 – x – 20 = 0
b) x^2 + x – 20 = 0
c) x^2 + 9x + 20 = 0
d) x^2 – 9x + 20 = 0

Answer:

a) x^2 – x – 20 = 0

Explanation:

Using the sum and product of roots, the equation is x^2 – (sum of roots)x + product of roots = 0.

5. The nature of the roots of the equation 2x^2 – 8x + 8 = 0 is:

a) Real and equal
b) Real and distinct
c) Imaginary
d) None of the above

Answer:

a) Real and equal

Explanation:

Discriminant = b^2 – 4ac = 64 – 64 = 0. Hence, roots are real and equal.

6. For the quadratic equation ax^2 + bx + c = 0, if a > 0 and the discriminant is greater than 0, the parabola:

a) Opens upwards and intersects the x-axis at two distinct points.
b) Opens downwards and intersects the x-axis at two distinct points.
c) Opens upwards and touches the x-axis.
d) Opens downwards and touches the x-axis.

Answer:

a) Opens upwards and intersects the x-axis at two distinct points.

Explanation:

Positive 'a' means the parabola opens upwards and discriminant > 0 means real and distinct roots.

7. The sum of the roots of the equation 3x^2 + 5x – 2 = 0 is:

a) -5/3
b) 5/3
c) 2/5
d) -2/5

Answer:

a) -5/3

Explanation:

Sum of the roots = -b/a = -5/3.

8. If one root of the quadratic equation kx^2 – 14x + 8 = 0 is 2, then the value of k is:

a) 3
b) 4
c) 5
d) 6

Answer:

c) 5

Explanation:

For x=2 to be a root, 2k – 14 + 8 = 0. Solving for k, we get k = 5.

9. The product of the roots of the equation x^2 + x + 1 = 0 is:

a) 1
b) -1
c) 0
d) Not defined

Answer:

b) -1

Explanation:

Product of the roots = c/a = 1/1 = 1.

10. For the equation ax^2 + bx + c = 0, if one root is the square of the other, then:

a) c = a^2b
b) b = ac
c) c = b^2/4a
d) a = c/b

Answer:

c) c = b^2/4a

Explanation:

Let the roots be α and α^2. Sum = α + α^2 = -b/a and product = α^3 = c/a. Using these relations, we get c = b^2/4a.

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