Class 8 Maths MCQ – Algebraic Expressions and Identities

1. Which of the following is a binomial?

a) 3x
b) x + 2y
c) x^2 + 2xy + y^2
d) x^2y

Answer:

b) x + 2y

Explanation:

A binomial consists of two terms. In this case, x and 2y.

2. What is the coefficient of x in the expression 3x^2 – 5x + 7?

a) 3
b) -5
c) 7
d) 0

Answer:

b) -5

Explanation:

The coefficient of x is the number that multiplies the variable x. In this expression, -5 multiplies x.

3. If (a + b)^2 = a^2 + b^2 + 2ab, then (2 + 3)^2 is:

a) 25
b) 10
c) 13
d) 29

Answer:

a) 25

Explanation:

Using the given identity, (2 + 3)^2 = 2^2 + 3^2 + 2(2)(3) = 25.

4. The algebraic expression for the statement "y subtracted from 5" is:

a) y – 5
b) 5y
c) 5 – y
d) y/5

Answer:

c) 5 – y

Explanation:

The statement is asking for y to be subtracted from 5, which is represented as 5 – y.

5. Which of the following is a polynomial?

a) 1/x
b) x^2 + 2x – 3
c) 2^x
d) sqrt(x)

Answer:

b) x^2 + 2x – 3

Explanation:

A polynomial is an expression of more than two algebraic terms, especially the sum of several terms. Here, x^2 + 2x – 3 satisfies that definition.

6. The product of (x + 3) and (x – 3) is:

a) x^2 – 9
b) x^2 + 9
c) x^2 – 6x
d) x^2

Answer:

a) x^2 – 9

Explanation:

Using the identity (a+b)(a-b) = a^2 – b^2, we get (x+3)(x-3) = x^2 – 9.

7. Which of the following is not an algebraic identity?

a) (a+b)^2 = a^2 + b^2
b) a^2 – b^2 = (a+b)(a-b)
c) (a+b)^2 = a^2 + 2ab + b^2
d) a^3 + b^3 = (a+b)(a^2 – ab + b^2)

Answer:

a) (a+b)^2 = a^2 + b^2

Explanation:

The correct identity for (a+b)^2 is a^2 + 2ab + b^2.

8. Which of the following expressions has a degree of 2?

a) 3x^3 – 2x + 1
b) 4x^2y + y^2
c) x^5 + 2
d) x – 3

Answer:

b) 4x^2y + y^2

Explanation:

The degree of an expression is the highest power of its variable. In 4x^2y + y^2, the highest power is 2.

9. The value of (a+b)(a-b) is:

a) a^2 + b^2
b) a^2 – b^2
c) a^2
d) b^2

Answer:

b) a^2 – b^2

Explanation:

Using the identity (a+b)(a-b) = a^2 – b^2.

10. If p(x) = 3x^3 – x^2 + 4x – 7, then the degree of p(x) is:

a) 1
b) 2
c) 3
d) 4

Answer:

c) 3

Explanation:

The degree is the highest power of x in the polynomial. Here, the highest power of x is 3.

11. The constant term in the expression 4x^2 – 3x + 2 is:

a) 4
b) -3
c) 2
d) 0

Answer:

c) 2

Explanation:

The constant term is the term without a variable. In this expression, it's 2.

12. The sum of the coefficients in the expression 5x^3 – 4x^2 + 3x – 6 is:

a) 2
b) -2
c) -6
d) 8

Answer:

b) -2

Explanation:

The coefficients are 5, -4, 3, and -6. Their sum is -2.

13. If (a + b + c)^2 = a^2 + b^2 + c^2 + 2ab + 2bc + 2ca, what is (2 + 3 + 4)^2?

a) 81
b) 54
c) 36
d) 49

Answer:

a) 81

Explanation:

Using the given identity, (2 + 3 + 4)^2 = 2^2 + 3^2 + 4^2 + 2(2*3) + 2(3*4) + 2(4*2) = 81.

14. The expression formed by subtracting 3 from 4x is:

a) 4x – 3
b) 3 – 4x
c) 12x
d) x – 12

Answer:

a) 4x – 3

Explanation:

Subtracting 3 from 4x gives 4x – 3.

15. Which of the following is a term?

a) +
b) x^2
c) =
d) –

Answer:

b) x^2

Explanation:

A term is a single mathematical expression. x^2 is an example.

16. The product of (x + 5) and (x – 5) is:

a) x^2 – 25
b) x^2 + 25
c) x^2
d) 10x

Answer:

a) x^2 – 25

Explanation:

Using the identity (a+b)(a-b) = a^2 – b^2, we get (x+5)(x-5) = x^2 – 25.

17. An algebraic expression that has no like terms and cannot be simplified further is:

a) 4x + 3x
b) 5y – 2y^2
c) 3x^2 + 3x^2
d) 2x + y

Answer:

d) 2x + y

Explanation:

2x and y are not like terms and cannot be combined further.

18. The expression x^2y^2 is an example of:

a) Binomial
b) Monomial
c) Trinomial
d) Polynomial

Answer:

b) Monomial

Explanation:

The expression x^2y^2 has only one term, making it a monomial.

19. The expression 3x^2 – 4x + 7 is a:

a) Monomial
b) Binomial
c) Trinomial
d) Polynomial

Answer:

c) Trinomial

Explanation:

The expression has three terms, making it a trinomial.

20. If (x + y)^2 = x^2 + y^2 + 2xy, then (3 + 4)^2 is:

a) 49
b) 25
c) 21
d) 50

Answer:

a) 49

Explanation:

Using the given identity, (3 + 4)^2 = 3^2 + 4^2 + 2(3)(4) = 49.

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