Respuesta :
Answer:
Option D
422 − 382 = (42 + 38)(42 − 38) = (80)(4) = 320
Step-by-step explanation:
 Let us consider the following:-
 (a + b)(a - b)
 a^2 - ab + ab - b^2
 Since -ab+ab = 0
 Then what will be left is:
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   a^2 - b^2
 This is a proof that:
 (a + b)(a - b) is the same as a^2 - b^2
 Let's use actual figures to show this:-
  (5 + 3)(5 - 3)
  25 - 15 + 15 - 9
 - 15+15 is the same as + 15 - 15 = 0
 We will then be left with:
   25 - 9 = 16
  The fact is that we can achieve this same result from the product of their sum and difference.
 Since 5 + 3 = 8 and 5 - 3 = 2
 Then:  (8)(2) = 16
 Now, back to the question:
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42^2 - 38^2 can be evaluated using the difference of perfect square method which is simply finding their sum and their difference and then multiplying the two results:
422 − 382 = (42 + 38)(42 − 38)
 42 + 38 = 80
 42 - 38 = 4
  Â
 (80)(4) = 320
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