Which ordered pair in the form (x, y) is a solution of this equation? (x + 6)y = 9 4, 1) (2, 1) (3, 1) (12, 2)

(3, 1)

substitute each ordered pair into the left side of the equation and if equal to the right side then it is a solution

(4, 1 )

(4 + 6) × 1 = 10 × 1 = 10 ≠ 9 ← not a solution

(2, 1 )

(2 + 6 ) × 1 = 8 × 1 = 8 ≠ 9 ← not a solution

(3, 1 )

(3 + 6 ) × 1 = 9 × 1 = 9 ← hence a solution

(12, 2 )

(12 + 6 ) × 2 = 18 × 2 = 36 ≠ 9 ← not a solution

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!