Question

Find the value of(7 3/10)^2- (2 1/10)^2using appropriate formula

Answer 1

$\sf \textbf{Find \: the \: value \: of { \bigg(\dfrac{73}{10}\bigg) }^{2}\! \!\!- \: \!\bigg(\dfrac{21}{10} \bigg)^2 }$

Solution:

Identity: ( a )² - ( b )² = (a + b) (a - b)

⠀

⟹⠀$\sf \: { \bigg(\dfrac{73}{10} \bigg)}^{2} - \bigg( { \dfrac{21}{10}\bigg)}^{2}$

⠀⠀⠀⠀⠀⠀⠀⠀⠀

⟹⠀$\sf\bigg( \dfrac{73}{10} - \dfrac{21}{10} \bigg) \times \bigg( \dfrac{73}{10} + \dfrac{21}{10} \bigg)$

⠀⠀⠀⠀⠀⠀⠀⠀⠀

⟹⠀$\sf \: \dfrac{52}{10} \times \dfrac{94}{10}$

⠀⠀⠀⠀⠀⠀⠀⠀⠀

⟹⠀$\sf \dfrac{4888}{100}$

⠀

or 48.88

Know More:

There are four standard identities. We could obtain more identities by using the standard ones:

• (a + b)² = a² + 2ab + b²
• ( a - b)² = a² - 2ab + b²
• ( x + a)( x + b) = x² + (a+b)x + ab
• a² + b² = ( a + b) ( a - b )