Question

Please help !! thanks in advance :D

Answer 1

$CIRCLES$

◆ A little manipulation of the diagram
( as shown in the attachment ) 

Once you're done with this simple manipulation and the labeling, we get the equation : OB² + BC² = OC²

 • r² = ( r - 9 )² + 15² 

Solve this trivial equation to get : r = 17 

 • Radius = 17 is your final answer .
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Hope this helps you :)

Answer 2

Answer:

a) 17

Step-by-step explanation:

Look at the picture.

We have the right triangle (red). Use the Pythagorean theorem:

$leg^2+leg^2=hypotenuse^2$

We have

$leg=15,\ leg=r-9,\ hypotenuse=r$

Substitute:

$15^2+(r-9)^2=r^2$       use (a - b)² = a² - 2ab + b²

$225+r^2-2(r)(9)+9^2=r^2$

$225+r^2-18r+81=r^2$         subtract r² from both sides

$306-18r=0$          subtract 306 from both sides

$-18r=-306$      divide both sides by (-18)

$r=17$