I beg for help where are the geniuses?

CB = sqrt62

Step-by-step explanation:

The pythagorean theorem will help with this! First take triangle ACD, AD^2 + CD^2 = AC^2. Plug in, AD^2 + 16 = 25. AD^2  = 9. AD = 3. I'm not exactly sure how to find DB, but I can assume it's double of AD< so 6. We know CD is 4, so  4^2 + 6^2 = CB^2. 16 + 36 = CB^2. CB = sqrt62

Sorry if this isn't exactly right, there's no exact way to find DB.

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step-by-step explanation:

hello from mrbilldoesmath!

answer:

25x^2 + 90x + 84

discussion:

mn(x) = m(n(x)) = m( 5x + 9) =

(5x + 9)^2 + 3 =>

25x^2 + 90x + 9^2 + 3 =

25x^2 + 90x + 84                 (as 9^2 = 9*9 = 81)

which is the second choice

regards,  

mrb

p.s.   i'll be on vacation from friday, dec 22 to jan 2, 2019. have a great new year!