1) \ D = (a + 3)^2 - 16 = a^2 + 6a + 9 - 16 = a^2 + 6a - 7 =\\\\ a^2 + 7a - a - 7 = a(a +7) - (a + 7) = (a - 1)(a + 7) &lt; 0\\\\ a_1 = 1, \&nbsp; a_2 = -7\\\\ a \in (-7; 1)