Pearson Geometry Common Core, 2011
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Pearson Geometry Common Core, 2011 View details
4. Similarity in Right Triangles
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Exercise 39 Page 466

Analyze what lengths you are given and use either the Right Triangle Similarity Theorem or one of its corollaries to write a proportion.

x=4

Practice makes perfect

Let's analyze the given right triangle so that we can find the value of x.

Consider the bigger triangle. We know the length of one of the segments of the hypotenuse, an expression for the length of the second segment of the hypotenuse, and an expression for the length of the leg adjacent to the second segment. Therefore, we can use a corollary of the Right Triangle Similarity Theorem to write a proportion.
Let's compare the theorem's corollary to the expressions in our figure. In our case, 5+x is the length of the hypotenuse, AC is x+2, and AD is x. AB/AC=AC/AD ⇔ 5+x/x+2=x+2/x Now we can use the Cross Product Property to find the value of x.
5+x/x+2=x+2/x
(5+x)x=(x+2)(x+2)
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Solve for x
5x+x^2=(x+2)(x+2)
5x+x^2=(x+2)^2
5x+x^2=x^2+4x+4
5x=4x+4
x=4