Ответ: 9 .
Объяснение:
φ = ( a ^,b) = 2π/3 ; | a | = 2 ; | b | = 3 ;
обчислюємо скалярний добуток :
( 5a + 3b )*( 3a - 2b ) = 15a² - 10a*b +9a*b - 6b² = 15 | a |² - a*b - 6 | b |² =
= 15* 2² - | a || b | *cos2π/3 - 6* 3² = 60 + 2 * 3 *cosπ/3 - 54 = 6 + 6* 1/2 = 6 + 3 = 9 ;
( 5a + 3b )*( 3a - 2b ) = 9 .
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Ответ: 9 .
Объяснение:
φ = ( a ^,b) = 2π/3 ; | a | = 2 ; | b | = 3 ;
обчислюємо скалярний добуток :
( 5a + 3b )*( 3a - 2b ) = 15a² - 10a*b +9a*b - 6b² = 15 | a |² - a*b - 6 | b |² =
= 15* 2² - | a || b | *cos2π/3 - 6* 3² = 60 + 2 * 3 *cosπ/3 - 54 = 6 + 6* 1/2 = 6 + 3 = 9 ;
( 5a + 3b )*( 3a - 2b ) = 9 .