Need help- Circle and Right triangle question

[kec21631]

I need help on problem #39 in the picture.
I tried to use the pythagorean theorem to solve it and I got:
64 + r^2 = 16 + r^2
The problem is, if I do it like that I end up eliminating the variable.

Please let me know if you have any idea on how I can solve this problem.

Thanks!

[stapel_eliz]

I need help on problem #39 in the picture.
I tried to use the pythagorean theorem to solve it and I got:
64 + r^2 = 16 + r^2

Hint: (4 + r)² is not equal to 4² + r².

. . . . .Multiplying Polynomials

[kec21631]

Oh! I get it now, thanks!