Using (x+a)(x+b)=x²+(a+b)x+ab, find (i) 103 x 104 (ii) 5.1 x 5.2

(i) 103 x 104 = (100 + 3) x (100 + 4) = (100)² +(3+4)x100+3×4
[Using identity (x+a) (x+b) =x²+(a+b)x+ab]
= 10000 + 7 x 100 + 12 = 10000 + 700 + 12 = 10712
(ii) 5.1 x 5.2 = (5 + 0.1) x (5 + 0.2) = (5)²+(0.1+0.2)x5+0.1×0.2
[Using identity (x+a) (x+b) =x²+(a+b)x+ab]
= 25 + 0.3 x 5 + 0.02 = 25 + 1.5 + 0.02 = 26.52

Class 8 Maths Chapter 9 Exercise 9.5 Solution in Video

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