Dr. Lizardo writes down a sequence of $n$ letters, where each letter is A, B, or C, and the letter A appears an even number of times. How many different sequences could Dr. Lizardo have written down?

use this formula:

p(a\b) = p(a and b)/p(b).

take it from here.

i think the answer is b.

step-by-step explanation:

not 100% sure though.

stop cheating

step-by-step explanation:

answer

d. 10

explanation

the distance from point y to wx is the height of the triangle.

using pythagoras theorem,

group similar terms to get,

this implies that,

take positive square root of both sides to get,

this implies that,