Roads are being built to connect three cities. if city a and city b are connected by a 20 mile road and city b and and city c are connected by a 6 mile road, which of the following length could the road between city c and city a be?

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!

x:       y:  

-1         4

0         4

1         6

2         18

3         20