577 views
4 votes
Solve the inequality, write the answer in interval notation.

Solve the inequality, write the answer in interval notation.-example-1
User Sauron
by
5.5k points

1 Answer

4 votes

9514 1404 393

Answer:

(-∞, 2-√7) ∪ (2+√7, ∞)

Explanation:

The factored form of a polynomial is helpful for solving related inequalities. For quadratics with two real zeros, the sign changes at each zero. If the leading coefficient is positive, the sign is positive to for x-values "outside" either zero, and is negative between the zeros.

Your inequality can be written in standard form as ...

x² -4x -3 > 0

x² -4x +4 -7 > 0

(x -2 -√7)(x -2 +√7) > 0 . . . . . factor the difference of squares (x-2)² -7

The zeros are at x=2-√7 and x=2+√7, so the product of these factors will be positive for x < 2-√7 and x > 2+√7. The solution in interval notation is ...

(-∞, 2-√7) ∪ (2+√7, ∞)

_____

Additional comment

We suspect a typo in the problem statement. If it were to read ... > -3, then the zeros would be at 1 and 3, and the solution would be (-∞, 1)∪(3, ∞).

Solve the inequality, write the answer in interval notation.-example-1
User Mamut
by
6.1k points