\[y = x^{2} - 6x - 7 =\]
\[= x^{2} - 6x + 9 - 16 =\]
\[= (x - 3)^{2} - 16;\]
\[y > 0\ при\ \ x < - 1;x > 7;\]
\[y < 0\ при\ - 1 < x < 7.\]