Answer:
I have exactly 5,621 dominoes, and, including myself, 23 people to set them all up. How many dominoes will each person set up?
Answer:
4x² -20x +61
Step-by-step explanation:
the quadratic equation can be written as (x-root1)(x-root2)
(x-(5/2) -3i) (x-(5/2)+3i), distribute
x² -(5/2)x +3xi -(5/2)x + 25/4 -(15/2)i -3xi +(15/2)i -9i², simplify
x² -(5/2)x -(5/2)x + 25/4 -9i², use the fact that i² =(√-1)² = -1 and substitute i²
x² -(5/2)x -(5/2)x + 25/4 +9, combine like terms and rewrite 9 as 36/4
x² -(10/2)x +25/4 + 36/4, combine like terms and simplify
x² -5x +61/4 is the quadratic expression yet it does not have integer coefficients so multiply by 4 to have all coefficients integers
4x² -20x +61
You figure out how long it would take a car traveling at 25 mph
to cover 360 ft. Any driver who does it in less time is speeding.
(25 mi/hr) · (5,280 ft/mile) · (1 hr / 3,600 sec)
= (25 · 5280 / 3600) ft/sec = (36 and 2/3) feet per second.
To cover 360 ft at 25 mph, it would take
360 ft / (36 and 2/3 ft/sec) = 9.82 seconds .
Anybody who covers the 360 feet in less than 9.82 seconds
is moving faster than 25 mph.
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If you're interested, here's how to do it in the other direction:
Let's say a car covers the 360 feet in ' S ' seconds.
What's the speed of the car ?
(360 ft / S sec) · (1 mile / 5280 feet) · (3600 sec/hour)
= (360 · 3600) / (S · 5280) mile/hour
= 245.5 / S miles per hour .
The teacher timed one car crossing both strips in 7.0 seconds.
How fast was that car traveling ?
245.5 / 7.0 = 35.1 miles per hour
Another teacher timed another car that took 9.82 seconds to cross
both strips. How fast was this car traveling ?
245.5 / 9.82 = 25 miles per hour