Respuesta :

ghanami
hello : 
by identity : (a-b)² = a² +b² -2ab
(x√7-3√8)(x√7-3√8) = (x√7-3√8)² = (x√7)²+(3√8)² -2(x√7)(3√8)
                                                    =7x²+72 -6x√56
                                                     = 7x²+72-6x√(14×4)
                                                     = 7x²+72-12x√(14).because  :√(14×4)=2√14
Answer B

In the given option Option B is the correct answer 7 x² + 72 - 12√14 x .

What is an Identity ?

An identity is an equation which is always true, no matter what values are substituted.

(a-b)² = a² + b² -2ab

here the given expression is

(x√7-3√8)(x√7-3√8)

here a = x√7

and b = 3√8

(a-b)² =  (x√7-3√8)²

(x√7-3√8)² =  (x√7)² + (3√8)² - 2 *x√7 *3√8

(x√7-3√8)² = 7 x² + 72 - 12√14 x

Therefore In the given option Option B is the correct answer 7 x² + 72 - 12√14 x .

To know more about Identity

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