NEED IN NEXT HOUR solve the following equation: 20= 4t -5t^2

2/5 ±i4/5sqrt(6)= t

Step-by-step explanation:

20= 4t -5t^2

Rewriting

20 = -5t^2 +4t

Divide by -5

20 = -5t^2 +4t

20/-5 = -5/-5t^2 +4/-5t

-4 = t^2 -4/5 t

Complete the square

Take the coefficient of t

-4/5

Divide by 2

-4/10 = -2/5

Square it

(-2/5)^2 = 4/25

Add to each side

-4 +4/25 = t^2 -4/5 t + 4/25

-100/25+4/25 = ( t-2/5)^2

-96/25 = ( t-2/5)^2

Take the square root of each side

sqrt(-96/25) = sqrt(( t-2/5)^2)

±isqrt(96/25)=( t-2/5)

±i4/5sqrt(6)=( t-2/5)

Add 2/5 to each side

2/5 ±i4/5sqrt(6)= t

54 kilometers per hour

step-by-step explanation:

according to rules:

1 km = 1000 meter

which means that 1 meter = 1/1000 km

1 hour = 3600 second [ as 1 hour = 60 min = 60 *60 seconds ]

which means that 1 second = 1/3600 hour

therefore, 1 kilometer/hour =

thus to convert 15 meter per second to kilometer per hour, we multiply 15 to 3.6 kilometer/hour.

15 meter/second=   which is the required answer.