Solving Radical Inequalities

MathematicsRadical InequalitiesMediumSTEM

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$$2 - \frac{2x}{3} \geq \sqrt{x + 4}$$

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Step by Step Written Solution

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Step 1

In this exercise, we'll solve a radical inequality. We are given two minus two x over three is greater than or equal to the square root of x plus four.

Solving a Radical Inequality

$$2 - \frac{2x}{3} \geq \sqrt{x+4}$$
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Step 2

Solving radical inequalities requires two main considerations: identifying the domain for which the root is defined, and ensuring both sides are handled correctly when squaring.


1. Domain Constraint

The term inside the square root must be non-negative.

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Step 3

So, x plus four must be greater than or equal to zero.

$$x + 4 \geq 0$$
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Step 4

By subtracting four from both sides, our first condition is that x must be greater than or equal to negative four.

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Step 5

Now, notice that the square root is always non-negative. For the left side to be greater than or equal to it, the left side must also be non-negative.

2. Sign Constraint

$$2 - \frac{2x}{3} \geq 0$$
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Step 6

We rearrange this to isolate x. Multiplying by three, we get six minus two x is greater than or equal to zero.

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Step 7

Then, six is greater than or equal to two x, which means x must be less than or equal to three.

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Step 8

With our domain and sign constraints established, we can safely square both sides of the original inequality.

Squaring the Inequality

Constraints: $-4 \leq x \leq 3$

$$(2 - \frac{2x}{3})^2 \geq (\sqrt{x+4})^2$$
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Step 9

Let's expand the left side using the binomial square formula.

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About This Question

Subject
Mathematics
Topic
Radical Inequalities
Difficulty
Medium
Exam
STEM
Question Type
Open Ended

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