Step-by-step explanation:
3a^2+24a+45=0
×3/3( first ×3)
9a^2+24(3a)+135=0
(3a+15)(3a+9)=0
now /3
3(a+5)(a+3)
a=-5✓
a=-3✓
Answer:
His average speed was of 10.42 m/s
Step-by-step explanation:
We use the following relation to solve this question:

In which v is the velocity(in m/s), d is the distance(in meters), and t is the time, in seconds.
Usain Bolt of Jamaica set a world record in 2009 for the 200- meter dash with a time of 19.19 seconds.
This means that 
So his average speed was of:

His average speed was of 10.42 m/s
Answer:
see explanation
Step-by-step explanation:
← evaluate
using calculator
=
= 
= 1.762.....
≈ 1.8 ( to 1 dec. place )
Group x terms
(2x^2+8x)-12=0
undistribute 2
2(x^2+4x)-12=0
take 1/2 of 4 and square it, add negative and positive of it insde (2^2=4)
2(x^2+4x+4-4)-12=0
factor perfect square
2((x+2)^2-4)-12=0
distribute
2(x+2)^2-8-12=0
2(x+2)^2-20=0
add 20 to both sides
2(x+2)^2=20
divide both sides by 2
(x+2)^2=10
sqrt both sides, remember to take positive and negative root
x+2=+/-√10
minus 2 both sides
x=-2+√10 and -2-√10