2-3*16=2-48=-46
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X^2 - 14x + 13 = 0
x1 + x2 = 14
x1 * x2 = 13
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x^2 + 12x + 35 = 0
x1 + x2 = - 12
x1 * x2 = 35
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7x^2 - 2x - 14 = 0
x1 + x2 = 2 / 7
x1 * x2 = ( - 14 ) / 7 = - 2
Решение
cos²(a/2) = (1 + cosa)/2
(1 + cosa)/2 = (1 + 0,6)/2 = 1,6 / 2 = 0,8