Mister Exam

Other calculators

sqrt(x^2-x-1)>sqrt(x+7) inequation

A inequation with variable

The solution

You have entered [src]
   ____________            
  /  2              _______
\/  x  - x - 1  > \/ x + 7 
$$\sqrt{x^{2} - x - 1} > \sqrt{x + 7}$$
sqrt(x^2 - x - 1*1) > sqrt(x + 7)
Detail solution
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:
$$x < -2$$
$$x > 4$$
Solving inequality on a graph
Rapid solution [src]
Or(And(-7 <= x, x < -2), And(4 < x, x < oo))
$$\left(-7 \leq x \wedge x < -2\right) \vee \left(4 < x \wedge x < \infty\right)$$
((-7 <= x)∧(x < -2))∨((4 < x)∧(x < oo))
Rapid solution 2 [src]
[-7, -2) U (4, oo)
$$x\ in\ \left[-7, -2\right) \cup \left(4, \infty\right)$$
x in Union(Interval.Ropen(-7, -2), Interval.open(4, oo))