Question

If c = 3k + 4 and d = 7 + 9k^2, what is d in terms of c?

a) c^2 + 8c + 23
b) c^2 - 8c + 23
c) 9c^2 - 108c +144
d) 9c^2 - 108c + 148
e) 9c^2 + 108c + 148

Answer 1

Explanation:

c = 3k + 4

c - 4 = 3k

k = (c-4)/3

this we use in the second equation

d = 7 + 9k² = 7 + 9((c-4)/3)² = 7 + 9((c² - 8c + 16)/9) =

= 7 + c² - 8c + 16 = c² - 8c + 23