## Exercise 13 A

**Multiply mentally and write only the products for each of the following .**

#### Question 1

**(x+4)(x+2)**

Sol :

#### Question 2

**(a+1)(a+8)**

#### Question 3

**(c+3)(c+2)**

#### Question 4

**(b-2)(b-5)**

#### Question 5

**(n-1)(n-6)**

#### Question 6

**(3-x)(5-x)**

#### Question 7

**(y-7)(y+3)**

#### Question 8

**(m+3)(m-2)**

#### Question 9

**(x-4)(x+6)**

#### Question 10

**(p+10)(p-9)**

#### Question 11

**(xy+6)(xy-5)**

#### Question 12

**(5-xy)(3+xy)**

#### Question 13

**(x ^{2}+3)(x^{2}+6)**

#### Question 14

**(4-x ^{2})(10+x^{2})**

#### Question 15

**(ab-13)(ab-4)**

#### Question 16

**(2x+3)(3x+2)**

#### Question 17

**(4x+7)(5x+6)**

#### Question 18

**(7x+1)(x+3)**

#### Question 19

**(2a ^{2}+3b^{2})(2a^{2}-5b^{2})**

#### Question 20

**(2x ^{2}-7y^{2})(3x^{2}+8y^{2})**

#### Question 21

**(i) (x+17)(x+2)**

**(ii) (x+1)(3-x)**

**(iii) (x-p)(x-q)**

**(iv) (2+3x)(3-5x)**

**(v) (5-x)(x+8)**

**(vi) (px-1)(px-1)**