david tiene libros en diferentes idiomas. se sabe que todos menos tres son libros en alemán, que todos menos tres son libros en italiano y que todos menos tres son libros en francés. El resto son libros en español ¿cuántos libros en español tiene David?​

, and

for

step-by-step explanation:

we can analyze the pattern at which the terms increase. let us denote , , , so that we can call

note the following:

the pattern: to get the next term value, we just add the next term number (e.g. 1st, 2nd, to the previous term value (term values are the given numbers in the question, 1, 3, 6, 10, 15,

from , to get to , we add

from , to get to , we add

etc.

we need to form a recursive formula, a formula that has the next term as a function of the previous term. so a possible recursive formula can be

, and for

ion

step-by-step explanation:

ion ion ion ion ion ion ion ion ion ion ion

sounds & other waves originate from any vibrating object