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Can someone please help me with this question? I really don't get it. Your help would be much appreciated. :) What is the length of CD to the nearest tenth?

Can someone please help me with this question? I really don't get it. Your help would-example-1

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3 votes

Answer:

5.7

Explanation:

The altitude of a right triangle divides it into two smaller triangles, all three of which are similar.

ΔABC ~ ΔADB ~ ΔBDC

Writing and solving a proportion:

AD / BD = BD / CD

(x + 3) / 5 = 5 / (2x + 3)

(x + 3) (2x + 3) = 25

2x² + 9x + 9 = 25

2x² + 9x − 16 = 0

x = [ -9 ± √(81 − 4(2)(-16)) ] / 2(2)

x = [ -9 ± √(81 + 128) ] / 4

x = (-9 ± √209) / 4

x = -5.86 or 1.36

Since x can't be -5.86, x = 1.36. So the length of CD is:

CD = 2(1.36) + 3

CD = 5.7

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