task/31614215
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* * * (a-b)(a²+ab+b²) =a³ - b³ ; (a-b)(a+b) =a² - b² * * *
(2x-7)(49+14x+4x²)+343-4(2x-1)(2x+1) =
(2x-7)( (2x)²+2x*7+7²)+343 - 4( (2x)²-1²) =
(2x)³ -7³ +343 - 4(4x²- 1) = 8x³ -343 +343 - 16x²+4 = 8x³ - 16x²+ 4 =
значение выражения при x= -0.5 = -1/2
8x³ - 16x²+ 4 = || x = - 1/2 || = 8*(-1/2)³ -16*(-1/2)² +4 = 8*(-1/8) - 16*1/4 + 4 =
-1 - 4 + 4 = - 1