Question

Ming throws a stone off a bridge into a river below.

Answer 1

Answer:

1 seconds after being thrown, the stone reaches its max height

Step-by-step explanation:

The parabolic (quadratic) equation is:

$h(x)=-5(x-1)^2+45$

Lets expand this in the form $ax^2+bx+c$, so we have:

$h(x)=-5(x-1)^2+45\\h(x)=-5(x^2-2x+1)+45\\h(x)=-5x^2+10x-5+45\\h(x)=-5x^2+10x+40$

We can say the values of a,b, and c, now to be:

a = -5

b = 10

c = 40

The number of seconds at which the max would occur is given by the point, x, at:

$x=-\frac{b}{2a}$

We know a and b, let's find the seconds, x,

$x=-\frac{b}{2a}=-\frac{10}{2(-5)}=-\frac{10}{-10}=--1=1$

Hence,

1 seconds after being thrown, the stone reach its max height

Answer 2

Answer:

1 second

Step-by-step explanation: