Algebraic expressions are mathematical expressions that consists of numbers, variables and mathematical operators.

Terms, factors and coefficients

• Factors: If algebraic expressions are expressed as the product of numbers, variables or expressions, then each of these numbers and expressions is called the factor of algebraic expressions.

• Multiplication of algebraic expressions

• Product of two monomials = (product of their numerical coefficients) × (product of their variable parts)

Example 1: 1ab and -2a²b³

SOLUTION: (1ab) × (-2a²b³)

= {1 × (-2)} × {ab × a²b³}

= -2 x a1+2 x b1+3

= -2a³b⁴.

• Multiplying a polynomial by a polynomial:

Suppose (x + y) and (p + q) are two polynomials. By using the distributive property of multiplication over addition twice, we may find their product as given below.

EXAMPLE 3: Multiply (1a³ – 2a² – a + 3) by (4 – 5a + 6a2)

SOLUTION: Arranging the terms of the given polynomials in descending power of a and then multiplying:

1a³ – 2a² – a + 3

× (4 – 5a + 6a²)
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6a⁵ - 12a⁴ – 6a³ + 18a² multiplication by 6a2.

- 5a⁴ + 10a³ + 5a² – 15a multiplication by -5a.

+ 4a³ – 8a² - 4a + 12 multiplication by 4.
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6a⁵ – 17a⁴ + 8a³ + 15a² – 19a + 12 multiplication by (4 – 5a + 6a²)
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Identities and its applications

• Some standard identities are:

EXAMPLE 1: Expand (a – 2b)3 using standard algebraic identities.

SOLUTION: (a– 2b)3 is of the form (a-b)3 where a = a and b = 2b. So we have,

(a – 2b)3 = (a)3 – (2b)3– 3(a)(2b)(a – 2b) = a3 – 8b3 – 6a2b + 12ab2 [ANS]

EXAMPLE 2: Find . Given = 12 and ab=3.

SOLUTION:

Practice these questions

Q1) Multiply the following:
a) 11x2y and 3 b)12 and 33 c)4 and 6

Q2) Find the value of when

Q3) Simplify the following:
a) (x+2y)(3x+4y) – (5x+6y)(7x+8y) b)(9a+10b)(2x+3y) – (4a+5b)(6c+7d)

Q4) Find the product of the following using identities:
a)(8x+9y)(8x-9y) b)(10x+11y+23z)2 c)(45a-6b)3 d)(7a+8b)3

Q5) Simplify using identities:
a)121 x 121 – 10012 b)9992 c)1012 d)

Q6) If , find the value of .

Q7) Find the value of x if 12x=

Q8) Tick the pair of like terms:

Q9) If , find the value of .

Recap

• Algebraic expressions are mathematical expressions that consists of numbers, variables and mathematical operators.
• If algebraic expressions are expressed as the product of numbers, variables or expressions, then each of these numbers and expressions is called the factor of algebraic expressions.
• Algebraic expressions which contain one non-zero term only are called monomials.

Algebraic expressions which contain two non-zero terms are called binomials.