f(x) = 20x² - 18x - 25
f(-1) = 20(-1)² - 18(-1) - 25
= 20 + 18 - 25
= 13
Cody ALONE = 8 hours
Kaitlyn ALONE = 6 hours
Let Joseph ALONE take j hours
Cody ALONE in 1 HOUR = 1/8 of the work Kaitlyn ALONE in 1 hour = 1/6 of the work Joseph ALONE in 1 HOUR = 1/j of the work
Since TOGETHER they take X hours, in 1 hour TOGETHER they complete 1 / X of the work
1/8 + 1/6 + 1/j = 1/X
1/j = 1/X - 1/8 - 1/6 = (24 - 3X - 4X ) /24X = (24 - 7X ) / 24X
j = 24X / ( 24- 7X )
After completing the work value of X will be known , calculate j from the above formula ANSWER
Answer:
x = 9
Step-by-step explanation:
23 - 5 = 18
18 ÷ 2 = 9......
