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Solve for [tex]x[/tex], where [tex]x[/tex] is a real number.

[tex] x = \sqrt{x + 30} [/tex]

Sagot :

To solve the equation [tex]\(x = \sqrt{x + 30}\)[/tex] for [tex]\(x\)[/tex], follow these steps:

1. Isolate the square root: The square root is already isolated in the given equation [tex]\(x = \sqrt{x + 30}\)[/tex].

2. Square both sides to eliminate the square root. Squaring both sides of the equation yields:
[tex]\[ x^2 = (\sqrt{x + 30})^2 \][/tex]
Which simplifies to:
[tex]\[ x^2 = x + 30 \][/tex]

3. Rearrange the equation to form a standard quadratic equation. To do this, move all terms to one side of the equation:
[tex]\[ x^2 - x - 30 = 0 \][/tex]

4. Factor the quadratic equation [tex]\(x^2 - x - 30 = 0\)[/tex]. To factor this, we need to find two numbers that multiply to [tex]\(-30\)[/tex] and add up to [tex]\(-1\)[/tex]. Those numbers are [tex]\(6\)[/tex] and [tex]\(-5\)[/tex]:
[tex]\[ x^2 - x - 30 = (x - 6)(x + 5) = 0 \][/tex]

5. Set each factor equal to zero to solve for [tex]\(x\)[/tex]:
[tex]\[ x - 6 = 0 \quad \text{or} \quad x + 5 = 0 \][/tex]

6. Solve each equation:
[tex]\[ x - 6 = 0 \implies x = 6 \][/tex]
[tex]\[ x + 5 = 0 \implies x = -5 \][/tex]

7. Check each potential solution in the original equation to ensure they are valid.

- For [tex]\(x = 6\)[/tex]:
[tex]\[ 6 = \sqrt{6 + 30} \][/tex]
[tex]\[ 6 = \sqrt{36} \][/tex]
[tex]\[ 6 = 6 \][/tex]
This is true.

- For [tex]\(x = -5\)[/tex]:
[tex]\[ -5 = \sqrt{-5 + 30} \][/tex]
[tex]\[ -5 = \sqrt{25} \][/tex]
[tex]\[ -5 = 5 \][/tex]
This is false, as [tex]\(-5\)[/tex] does not equal [tex]\(5\)[/tex].

Hence, the only valid solution is:

[tex]\[ x = 6 \][/tex]