In Mrs. Williams class there are 13 students. They each have 4 pieces of white paper. Some of the students, s, also have 3 pieces of blue paper each. In all, the students have 64 pieces of paper. Which equation represents this situation?
A. (13 × 3) + s = 64
B. (s × 3) + 13 = 64
C. s × 3 = 64
D. (13 × 4) + (s × 3) = 64

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!