Question

(5c - 6) (5c + 6) - (5c - 6)² при c = 13

Answer 1

(5c - 6)(5c + 6) - (5c - 6)² = 25c² - 36 - (25c² - 60c + 36) =

= 25c² - 36 - 25c² + 60c - 36 = 60c - 72

если c = 13 , то :  60 * 13 - 72 = 780 - 72 = 708

Answer 2

To evaluate the expression (5c - 6) (5c + 6) - (5c - 6)² when c = 13, we first substitute 13 for c:

(5c - 6) (5c + 6) - (5c - 6)² = (5(13) - 6) (5(13) + 6) - (5(13) - 6)²

Simplifying the expression inside the parentheses, we get:

= (59)(71) - (59)²

Next, we can calculate 59 squared:

= (59)(71) - 3481

Multiplying 59 and 71 gives:

= 4189 - 3481

Finally, we can subtract 3481 from 4189:

= 708

Therefore, (5c - 6) (5c + 6) - (5c - 6)² when c = 13 is equal to 708.