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In the proof of the Law of Cosines, the equation [tex]c^2 = h^2 + (b-x)^2[/tex] was created using the Pythagorean theorem. Which equation is a result of expanding [tex](b-x)^2[/tex]?

A. [tex]c^2 = h^2 + b^2 - x^2[/tex]
B. [tex]c^2 = h^2 + b^2 - 2bx + x^2[/tex]
C. [tex]c^2 = h^2 + b^2 + x^2[/tex]
D. [tex]c^2 = h^2 + b^2 - 2bx - x^2[/tex]


Sagot :

To solve this problem, we need to correctly apply the algebraic expansion of \((b - x)^2\) and then substitute it into the given equation \(c^2 = h^2 + (b - x)^2\).

### Step-by-Step Solution:

1. Start with the expression \((b - x)^2\):
[tex]\[(b - x)^2\][/tex]

2. Expand this expression using the formula \((a - b)^2 = a^2 - 2ab + b^2\) where \(a = b\) and \(b = x\):
[tex]\[ (b - x)^2 = b^2 - 2bx + x^2 \][/tex]

3. Substitute the expanded form of \((b - x)^2\) into the original equation \(c^2 = h^2 + (b - x)^2\):
[tex]\[ c^2 = h^2 + (b^2 - 2bx + x^2) \][/tex]

4. Combine like terms:
[tex]\[ c^2 = h^2 + b^2 - 2bx + x^2 \][/tex]

This is the expanded form of \((b - x)^2\) in the given equation.

### Conclusion:
The correct equation resulting from expanding \((b - x)^2\) and substituting it back into \(c^2 = h^2 + (b - x)^2\) is:
[tex]\[ c^2 = h^2 + b^2 - 2bx + x^2 \][/tex]

Thus, the correct answer is:
[tex]\[ \boxed{c^2 = h^2 + b^2 - 2 b x + x^2} \][/tex]
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