Question

subtract 3p-2q+r from 9p+2q and add the result to p2 -3p3+p-r​

Answer 1

− 4xy

− 8x2y

20xy2

− 12x3y

16x2y2

− 28x3y2

36x3y3

7x2y

14x3y

− 35x2y2

21x4y

− 28x3y2

49x4y2

− 63x4y3

− 9x2y2

− 18x3y2

45 x2y3

− 27x4y2

36x3y3

− 63x4y3

81x4y4

Page No 144:

Question 4:

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

(i) 5a, 3a2, 7a4 (ii) 2p, 4q, 8r (iii) xy, 2x2y, 2xy2

(iv) a, 2b, 3c

ANSWER:

We know that,

Volume = Length × Breadth × Height

(i) Volume = 5a × 3a2 × 7a4 = 5 × 3 × 7 × a × a2 × a4 = 105 a7

(ii) Volume = 2p × 4q × 8r = 2 × 4 × 8 × p × q × r = 64pqr

(iii) Volume = xy × 2x2y × 2xy2 = 2 × 2 × xy ×x2y × xy2 = 4x4y4

(iv) Volume = a × 2b × 3c = 2 × 3 × a × b × c = 6abc

Video Solution for algebraic expressions and identities (Page: 144 , Q.No.: 4)

NCERT Solution for Class 8 math - algebraic expressions and identities 144 , Question 4

Page No 144:

Question 5:

Obtain the product of

(i) xy, yz, zx (ii) a, − a2, a3 (iii) 2, 4y, 8y2, 16y3

(iv) a, 2b, 3c, 6abc (v) m, − mn, mnp

ANSWER:

(i) xy × yz × zx = x2y2z2

(ii) a × (− a2) × a3 = − a6

(iii) 2 × 4y × 8y2 × 16y3 = 2 × 4 × 8 × 16 × y × y2 × y3 = 1024 y6

(iv) a × 2b × 3c × 6abc = 2 × 3 × 6 × a × b × c × abc = 36a2b2c2

(v) m × (− mn) × mnp = − m3n2p

Page No 146:

Question 1:

Carry out the multiplication of the expressions in each of the following pairs.

(i) 4p, q + r (ii) ab, a − b (iii) a + b, 7a2b2

(iv) a2 − 9, 4a (v) pq + qr + rp, 0

ANSWER:

(i) (4p) × (q + r) = (4p × q) + (4p × r) = 4pq + 4pr

(ii) (ab) × (a − b) = (ab × a) + [ab × (− b)] = a2b − ab2

(iii) (a + b) × (7a2 b2) = (a × 7a2b2) + (b × 7a2b2) = 7a3b2 + 7a2b3

(iv) (a2 − 9) × (4a) = (a2 × 4a) + (− 9) × (4a) = 4a3 − 36a

(v) (pq + qr + rp) × 0 = (pq × 0) + (qr × 0) + (rp × 0) = 0

Page No 146:

Question 2:

Complete the table

---

First expression

Second Expression

Product

(i)

a

b + c + d

-

(ii)

x + y − 5

5 xy

-

(iii)

p

6p2 − 7p + 5

-

(iv)

4p2q2

p2 − q2

-

(v)

a + b + c

abc

-

ANSWER:

The table can be completed as follows.

-

First expression

Second Expression

Product

(i)

a

b + c + d

ab + ac + ad

(ii)

x