How to graph a parabola y = (x + 5)^2 - 3?

1 Answer
May 5, 2018

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Please read the explanation.

Explanation:

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The Vertex Form of a quadratic function is :

color(blue)(y=f(x)=a(x-h)^2+k, where color(green)(( h, k ) is the Vertex of the Parabola.

Quadratic Function is given in Vertex Form: color(red)(y = (x + 5)^2 - 3

color(brown)(h=-5 and k = -3

Vertex is at color(green)((h,k): color(blue)((-5, -3)

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Plot the Vertex and the color(red)((x,y) values from the data table.

To find the x-intercepts:

f(x)=(x+5)^2-3

Let f(x)=0

:. (x+5)^2-3 = 0

Add color(red)(3 to both sides:

(x+5)^2-3+color(red)(3)= 0+color(red)(3

(x+5)^2-cancel 3+color(red)(cancel 3)= 0+color(red)(3

(x+5)^2 = 3

Take Square root on both sides to simplify:

sqrt((x+5)^2) = sqrt(3)

(x+5) = +- sqrt(3)

Subtract color(red)(5) from both sides:

(x+5)-color(red)(5) = +- sqrt(3)-color(red)(5)

(x+cancel 5)-color(red)(cancel 5) = +- sqrt(3)-color(red)(5)

x=+-sqrt(3)-5

Hence, color(blue)(x=[sqrt(3)-5] is one solution and color(blue)(x=[-sqrt(3)-5] is the other.

Using a calculator,

color(blue)(x~~ -3.26795) is one solution.

color(blue)(x~~ -6.73205) is another solution.

Hence, x-intercepts are: x~~ -3.3, x~~ -6.7

Verify this solution by using graphs:

color(green)("Graph 1"

Graph of color(blue)(y=x^2

This is the Parent Graph.

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Use this graph to understand the behavior of the given quadratic function.

color(green)("Graph 2"

Graph of color(blue)(y = (x + 5)^2 - 3

Study the graphs of both the Parent function and the given function.

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Next, verify the x-intercepts:

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Hope it helps.