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Which equation can be rewritten as [tex]$x+4=x^2$[/tex]? Assume [tex]$x\ \textgreater \ 0$[/tex].

A. [tex]\sqrt{x}+2=x[/tex]
B. [tex]\sqrt{x+2}=x[/tex]
C. [tex]\sqrt{x+4}=x[/tex]
D. [tex]\sqrt{x^2+16}=x[/tex]


Sagot :

To determine which equation can be rewritten as [tex]\(x + 4 = x^2\)[/tex], we'll solve each equation step-by-step and see which one matches [tex]\(x + 4 = x^2\)[/tex].

### Equation 1: [tex]\(\sqrt{x} + 2 = x\)[/tex]

1. Start with the given equation:
[tex]\[ \sqrt{x} + 2 = x \][/tex]

2. Isolate the square root term:
[tex]\[ \sqrt{x} = x - 2 \][/tex]

3. Square both sides to eliminate the square root:
[tex]\[ (\sqrt{x})^2 = (x - 2)^2 \][/tex]
[tex]\[ x = x^2 - 4x + 4 \][/tex]

4. Rearrange the equation to standard quadratic form:
[tex]\[ 0 = x^2 - 5x + 4 \][/tex]
[tex]\[ x^2 - 5x + 4 = 0 \][/tex]

This equation is not equivalent to [tex]\(x + 4 = x^2\)[/tex].

### Equation 2: [tex]\(\sqrt{x+2} = x\)[/tex]

1. Start with the given equation:
[tex]\[ \sqrt{x+2} = x \][/tex]

2. Square both sides to eliminate the square root:
[tex]\[ (\sqrt{x+2})^2 = x^2 \][/tex]
[tex]\[ x + 2 = x^2 \][/tex]

3. Rearrange the equation to standard quadratic form:
[tex]\[ x^2 - x - 2 = 0 \][/tex]

This equation is not equivalent to [tex]\(x + 4 = x^2\)[/tex].

### Equation 3: [tex]\(\sqrt{x+4} = x\)[/tex]

1. Start with the given equation:
[tex]\[ \sqrt{x+4} = x \][/tex]

2. Square both sides to eliminate the square root:
[tex]\[ (\sqrt{x+4})^2 = x^2 \][/tex]
[tex]\[ x + 4 = x^2 \][/tex]

This equation is exactly [tex]\(x + 4 = x^2\)[/tex].

### Equation 4: [tex]\(\sqrt{x^2 + 16} = x\)[/tex]

1. Start with the given equation:
[tex]\[ \sqrt{x^2 + 16} = x \][/tex]

2. Square both sides to eliminate the square root:
[tex]\[ (\sqrt{x^2 + 16})^2 = x^2 \][/tex]
[tex]\[ x^2 + 16 = x^2 \][/tex]

This results in:
[tex]\[ 16 = 0 \][/tex]

This is a contradiction and cannot be true for any [tex]\(x\)[/tex].

Therefore, the equation that can be rewritten as [tex]\(x + 4 = x^2\)[/tex] is:

[tex]\[ \sqrt{x + 4} = x \][/tex]