Question

9.7x9.8 using identities evaluate​

Answer 1

Step-by-step explanation:

9.7 × 9.8

$= (9 + 0.7) \: (9 + 0.8) \\ \because \: we \: know \: that \: \\ (x + a)(x + b) = {x}^{2} + (a + b)x + a \times b \\ (9 + 0.7)(9 + 0.8) = {9}^{2} + (0.7 + 0.8)9 + 0.7 \times 0.8 \\ = 81 + 1.5 \times 9 + 0.56 \\ = 81 + 13.5 + 0.56 \\ = 95.06$

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Answer 2

Answer:

9.7 x 9.8 = 95.06

Step-by-step explanation:

9.7 x 9.8

$= (9.75 - 0.05)(9.75 + 0.05)$

$=9.75^2 - 0.05^2$  [∵ $a^2 - b^2 = (a + b)(a - b)$]

$=(10 - 0.25)^2 - 0.05^2$

$=10^2 - 2.10.(0.25) + 0.25^2 - 0.05^2$ [∵ $(a - b)^2 = a^2 - 2.a.b + b^2$]

=100 - 5 + 0.0625 - 0.0025

=95 + 0.06

=95.06