1st Example: first term 5, and ratio r = 2
5 , 10 , 20 , 40 , 80, ...
2nd Example: first term 5, and ratio r = - 2
5 , - 10 , +20 , -40, +80, ....
Answer:
x = 6 x = -7
Step-by-step explanation:
Subtract 12 from each side:
x^2 + x - 30 - 12 = 12 - 12
Simplify:
x^2 + x - 42 = 0
Solve with quadratic formula using both +/- after the first -1:
x = 
Simplify:
x = 6
x = -7
Search it on google it instantly pops up as C = 28.27 ft