Multiply: 12a + 5b by 7a − B - Mathematics


Multiply: 12a + 5b by 7a − b



(12a + 5b) (7a − b) = 12a (7a − b) + 5b (7a − b)

= 84a2 − 12ab + 35ab − 5b

= 84a2 + 23ab − 5b2

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Chapter 11: Algebraic Expressions - Exercise 11 (C) [Page 143]


Selina Concise Mathematics Class 8 ICSE
Chapter 11 Algebraic Expressions
Exercise 11 (C) | Q 1.09 | Page 143


Obtain the volume of a rectangular box with the following length, breadth, and height, respectively.

a, 2b, 3c

Obtain the product of a, − a2, a3

Express each of the following product as a monomials and verify the result for x = 1, y = 2:

\[\left( \frac{2}{5} a^2 b \right) \times \left( - 15 b^2 ac \right) \times \left( - \frac{1}{2} c^2 \right)\]

Multiply : 8ab2 by − 4a3b4

Multiply: −5cd2 by − 5cd2

Multiply: 4a and 6a + 7

Multiply: 2a2 − 5a − 4 and −3a

Multiply: 5a − 1 by 7a − 3

Multiply: abx, −3a2x and 7b2x3

Multiply: −3bx, −5xy and −7b3y2

Multiply: `-2/3"a"^7"b"^2` and `-9/4"a""b"^5`

Multiply: `2"a"^3-3"a"^2"b"` and `-1/2"ab"^2`

Multiply: `2"x"+1/2"y"` and `2"x"-1/2"y"`

Find the volume of each rectangular box with given length, breadth, and height.
  Length breadth height
(i) 2ax 3by 5cz
(ii) m2n n2p p2m
(iii) 2q 4q2 8q3

Solve: ( -3x2 ) × ( -4xy)

Solve: (-12x) × 3y2

Multiply (4x2 + 9) and (3x – 2)

The length of a rectangle is `1/3` of its breadth. If its perimeter is 64 m, then find the length and breadth of the rectangle.

A total of 90 currency notes, consisting only of ₹ 5 and ₹ 10 denominations, amount to ₹ 500. Find the number of notes in each denomination.

At present, Thenmozhi’s age is 5 years more than that of Murali’s age. Five years ago, the ratio of Thenmozhi’s age to Murali’s age was 3 : 2. Find their present ages.

Three consecutive integers, when taken in increasing order and multiplied by 2, 3 and 4 respectively, total up to 74. Find the three numbers.

Multiply the following:

15xy2, 17yz2 

Multiply the following: 

–3x2y, (5y – xy)

Multiply the following: 

abc, (bc + ca)

Multiply the following: 

x2y2z2, (xy – yz + zx)

Multiply the following: 

(p + 6), (q – 7)

Multiply the following: 

6mn, 0mn


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