You can model an arch at your school using the equation y=−0.9(x+3)(x−3), where x and y are measured in feet. The x-axis represents the ground. Find the width of the arch at ground level.

6 ft

Step-by-step explanation:

As we know that, the arch meet the ground are the value of x when y = 0

y=−0.9(x+3)(x−3)

<=> 0 = −0.9(x+3)(x−3)

<=> x=3 or x=-3  

So we have 2 coordinates: (3, 0) and (-3,0) and the distance between them is:

3 -(-3) = 6

=> The width of the arch at ground level is 6 ft

d) by the cross product property, ab^2 = bc multiplied by ad

step-by-step explanation:

we are given

in the given triangle abc

angle a is 90° and segment ad is perpendicular to segment bc

we can see that

triangle(abc) and triangle(abd) are similar because they have common side and same angle (90 degree)

so, triangles(abc) and abd are similar

since, they are similar

so, the ratio of their sides must be equal

we get

now, we can cross multiply

and we get

so, this could be step to prove it