A fountain on a lake sprays water in a parabolic arch modeled by the equation y = -0.3x2 + 3x. A beam of light modeled by the equation
-2x + 5.5y = 19.5 passes through the fountain to create a rainbow effect. If the beam cuts the water spray at points A and B, such that point B is at a higher level than point A, what distance from the ground level is point A?
A) 1.66 units
B) 4.15 units
C) 5.44 units
D) 6.14 units
E) 7.13 units

Respuesta :

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y=-.3x^2+3x 

....

-2x+5.5y=19.5

5.5y=19.5+2x

y=(19.5+2x)/5.5

When the light touches the parabola y=y so

(19.5+2x)/5.5=-.3x^2+3x  multiply both sides by 5.5

19.5+2x=-1.65x^2+16.5x  add 1.65x^2 to both sides

1.65x^2+2x+19.5=16.5x  subtract 16.5x from both sides

1.65x^2-14.5x+19.5=0

Using the quadratic equation for simplicity...

x=(14.5±√81.55)/3.3  we only need the lower point, or the smaller value of x

x≈1.657423  since:

y=(19.5+2x)/5.5

y≈4.15 units


Point A is at distance of 1.66 units from the ground level.

The correct answer is an option (A)

What is equation?

"It is a mathematical statement which consists of equal symbol between two algebraic expressions."

For given question,

A fountain on a lake sprays water in a parabolic arch modeled by the equation [tex]y = -0.3x^2 + 3x[/tex]

A beam of light modeled by the equation -2x + 5.5y = 19.5

We write the equation of a beam of light in terms of y.

⇒ -2x + 5.5y = 19.5

⇒ 5.5y = 19.5 +2x

⇒ [tex]y =\frac{19.5 +2x}{5.5}[/tex]

When a beam of light passes through the fountain,

[tex]\Rightarrow y=y\\\\\Rightarrow -0.3x^2 + 3x=\frac{19.5 +2x}{5.5}\\\\\Rightarrow -1.65x^2+16.5x=19.5+2x\\\\\Rightarrow 1.65x^2-14.5x+19.5=0\\\\\Rightarrow (x-7.1)(x-1.66)=0\\\\\Rightarrow x-7.1=0~~,~~x-1.66=0\\\\\Rightarrow x=7.1~~,~~x=1.66[/tex]

Point A is at lower level than point B.

This means, point A is at  the minimum distance from the ground level.

So, x = 1.66 units would be the distance between the ground level and the point A.

Therefore, point A is at distance of 1.66 units from the ground level.

The correct answer is an option (A)

Learn more about equation here:

https://brainly.com/question/13170101

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