Question

12.1
8.
Using (x + a) (x + b) = x? + (a + b) x + ab, find
(1) 103 * 104 (ii) 5.1 x 5.2
(iii) 103 x 98
(iv) 9.7 * 9.8​

Answer 1

Step-by-step explanation:

$(103) \times (104) \\ (100 + 3)(100 + 4) \\ 100 {}^{2} + (4 + 3)100 + 12$

$10000 + 700 + 12 \\ 10712$

Answer 2

Answer:

103 x 104

= (100 + 3)(100 + 4)

By using the formula  ,(x + a) (x + b) = x²+ (a + b) x + ab    

= 100² + (3 + 4)100 + (3×4)

= 10000 + 700 + 12

= 10712

 

2) 5.1 x 5.2

= (5 + 0.1)(5 + 0.2)

By using the formula  ,(x + a) (x + b) = x²+ (a + b) x + ab  

= 5² + (0.1+0.2)5 + (0.1×0.2)

= 25 + 1.5 + 0.02

= 26.52

 

3) 103 x 98

= (100 + 3)(100 - 2)

By using the formula  ,(x + a) (x + b) = x²+ (a + b) x + ab  

= 100² + (3-2)100 – (3×2)

= 10000 + 100 - 6

= 10094

Step-by-step explanation: