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21. Which one of the following is equivalent to the equation shown below?

[tex]\[ \frac{15}{x} - \frac{3}{x-7} \][/tex]

A. [tex]\(x(x-7)=45\)[/tex]

B. [tex]\(15(x-7)=3x\)[/tex]

C. [tex]\(15x=3(x-7)\)[/tex]

D. [tex]\(18=x+(x+7)\)[/tex]


Sagot :

Let's carefully analyze each given option to determine if any of them are equivalent to the original equation:

[tex]\[ \frac{15}{x} - \frac{3}{x-7} \][/tex]

### Option a)
[tex]\( x(x-7) = 45 \)[/tex]

Analyzing this, we clearly see it does not represent a form involving the fractions [tex]\(\frac{15}{x}\)[/tex] and [tex]\(\frac{3}{x-7}\)[/tex]. Instead, it establishes a product equal to 45 which does not align with the structure of our original equation.

### Option b)
[tex]\( 15(x-7) = 3x \)[/tex]

Expanding this option:
[tex]\[ 15x - 105 = 3x \][/tex]
Solving for [tex]\(x\)[/tex]:
[tex]\[ 15x - 3x = 105 \quad \Rightarrow \quad 12x = 105 \quad \Rightarrow \quad x = \frac{105}{12} \][/tex]
This resulting equation is not in the same form as the given equation involving fractions.

### Option c)
[tex]\( 15x = 3(x - 7) \)[/tex]

Expanding this, we get:
[tex]\[ 15x = 3x - 21 \][/tex]
Solving for [tex]\(x\)[/tex]:
[tex]\[ 15x - 3x = -21 \quad \Rightarrow \quad 12x = -21 \quad \Rightarrow \quad x = -\frac{21}{12} = -\frac{7}{4} \][/tex]
Again, this does not align with our initial equation's format with fractions.

### Option d)
[tex]\( 18 = x + (x + 7) \)[/tex]

Expanding this:
[tex]\[ 18 = x + x + 7 \quad \Rightarrow \quad 18 = 2x + 7 \quad \Rightarrow \quad 2x = 11 \quad \Rightarrow \quad x = \frac{11}{2} \][/tex]
This also does not match the original equation's structure.

### Conclusion

After carefully checking each of the options, none of them equate to the given equation:

[tex]\[ \frac{15}{x} - \frac{3}{x-7} \][/tex]

None of the provided options accurately reflect the initial equation involving the fractions. Therefore, the correct answer is:

[tex]\[ \boxed{\text{None of the given options}} \][/tex]