Given the inequality:
$$\sqrt{x^{2} - x - 1} > \sqrt{x + 7}$$
To solve this inequality, we must first solve the corresponding equation:
$$\sqrt{x^{2} - x - 1} = \sqrt{x + 7}$$
Solve:
$$x_{1} = -2$$
$$x_{2} = 4$$
$$x_{1} = -2$$
$$x_{2} = 4$$
This roots
$$x_{1} = -2$$
$$x_{2} = 4$$
is the points with change the sign of the inequality expression.
First define with the sign to the leftmost point:
$$x_{0} < x_{1}$$
For example, let's take the point
$$x_{0} = x_{1} - \frac{1}{10}$$
=
$$-2 - \frac{1}{10}$$
=
$$- \frac{21}{10}$$
substitute to the expression
$$\sqrt{x^{2} - x - 1} > \sqrt{x + 7}$$
$$\sqrt{\left(-1\right) 1 - - \frac{21}{10} + \left(- \frac{21}{10}\right)^{2}} > \sqrt{- \frac{21}{10} + 7}$$
_____ ____
\/ 551 7*\/ 10
------- > --------
10 10
one of the solutions of our inequality is:
$$x < -2$$
_____ _____
\ /
-------ο-------ο-------
x_1 x_2
Other solutions will get with the changeover to the next point
etc.
The answer:
$$x < -2$$
$$x > 4$$