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Recall the equation for a circle with center (h,k) and radius r. At what point in the first quadrant does not line with equation y=2x+4 intersects the circle with radius 4 and center (0,4)

Sagot :

Answer:

(1.79, 7.58)

Step-by-step explanation:

Standard form equation of a circle with center (h,k) and radius r is

[tex]\displaystyle{(x-h)^2+(y-k)^2=r^2}[/tex]

Use h = 0, k = 4 and r=4 to give

--> [tex]\displaystyle{(x-0)^2+(y-4)^2=4^2}[/tex]

--> [tex]x^2 + (y-4)^2 = 16[/tex]

[tex](y-4)^2 = y^2 -8y + 16[/tex]

The line is [tex]y = 2x + 4[/tex]

Substitute for this value of y in Equation (1)

[tex]x^2 + (2x + 4 - 4)^2 = 16[/tex]

[tex]x^2 + (2x)^2 = 16[/tex]

[tex]x^2 + 4x^2 = 16[/tex]

[tex]5x^2 = 16[/tex]

[tex]x^2 = \frac{16}{5}[/tex]

[tex]x = \pm \sqrt{\frac{16}{5}}[/tex]

[tex]x = \pm \frac{4}{\sqrt{5}}[/tex]

Since we are asked to find point of intersection only on the first quadrant, we ignore the negative value of x

So [tex]x = \frac{4}{\sqrt{5} } = 1.78885 = 1.79[/tex]  (rounded to 2 decimal places)

Substituting this value of x in [tex]y = 2x + 4[/tex]

[tex]y = 2(1.79) = 4 = 7.58[/tex]

So the intersection point is at

(1.79, 7.58)

See attached graph

View image Rvkacademic