Respuesta :
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
....
-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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