Using $a^{2} - b^{2} = (a + b) (a - b),$ find
${12.1}^{2} - {7.9}^{2}$

80

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84

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88

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Solution

The correct option is B $84$
${12.1}^{2} - {7.9}^{2} = (12.1 + 7.9) (12.1 - 7.9)$
$[U s i n g i d e n t i t y (a - b) (a + b) = a^{2} - b^{2}]$
$= 20.0 \times 4.2 = 84.0 = 84$

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Similar questions

a^{2} - b^{2} = (a + b) (a - b),

{12.1}^{2} - {7.9}^{2}

a^{2} - b^{2} = (a + b) (a - b)

{12.1}^{2} - {7.9}^{2}

a^{2} - b^{2} = (a + b) (a - b)

(i) 153^{2} - 147^{2} (i i) {12.1}^{2} - {7.9}^{2}

Using a²− b² = (a + b) (a − b), find

(i) 51² − 49² (ii) (1.02)² − (0.98)² (iii) 153² − 147²

(iv) 12.1² − 7.9²

a^{2} - b^{2} = (a + b) (a - b),

12^{2} - 8^{2}

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