Q : 8          Using  (x+a)(x+b)=x^2+(a+b)x+ab , find 

                  (iv) 9.7 \times 9.8

Answers (1)

We know,

(x+a)(x+b)=x^2+(a+b)x+ab

Using this formula,

9.7 \times 9.8 = (10 - 0.3)(10 - 0.2) = {10 + (-0.3)}{10 + (-0.2)}

Here x =10, a = -0.3, b = -0.2

\therefore 9.7 \times 9.8  = 10^2+((-0.3) + (-0.2))10+((-0.3)\times(-0.2))

= 100-5+0.06

= 95.06

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