Answer:
81
Step-by-step explanation:
(9x - 4)(9x + 4) = ax² - b
81x² - 36x + 36x - 16
= 81x² - 16
=> a = 81
Let the speed for the first 12 mi be x mi/h, the speed for 18 mi was (x+4) mi/h
thus given that
time=distance/speed
the average time will be:
3=(12+18)/(x+x+4)
3=30/(2x+4)
solving for x we get
3(2x+4)=30
6x+6=30
6x=24
x=4 mi/hr
Answer: 12 mi/hr
He will have made a hemisphere which is half of a sphere.
b= 63 and that is your answer
