All atoms of the same element: O have the same number of atoms
O have the same number of neutrons
O have the same number of electrons
have the same number of protons

last one

Step-by-step explanation:

All atoms of the same element will always have the same atomic number and since atomic number indicates the amount of protons in its nucleus the answer is "have the same number of protons).

The last one

Step-by-step explanation:

All atoms have to have the same number of electrons or else they are not classified as that element.

answer: no

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!