Since p = x² - 7, you can substitute/plug in p for x² - 7
So:
(x² - 7)² - 4x² + 28 = 5
(p)² - 4x² + 28 = 5 You can factor out -4 from (-4x² + 28)
p² - 4(x² - 7) = 5 Plug in p
p² - 4p = 5 Subtract 5
p² - 4p - 5 = 0 Your answer is C
Use a system of equations:
For his trip on the way there:
D = 7*s
For his trip on the way home you have:
D = 5*(s+18)
use substitution to solve
Multiply price per pound by total pounds:
2.50 x 3.5 = 8.75
Total cost = $8.75
