Maths-
General
Easy
Question
Find the axis of symmetry, vertex and y-intercept of the function
f(x) = -x2 - 2x – 5
Hint:
For a quadratic function is in standard form, f(x)=ax2+bx+c.
A vertical line passing through the vertex is called the axis of symmetry for the parabola.
Axis of symmetry x=−b/2a
Vertex The vertex of the parabola is located at a pair of coordinates which we will call (h, k). where h is value of x in axis of symmetry formula and k is f(h).
The y-intercept is the point where a graph crosses the y-axis. In other words, it is the value of y when x=0.
The correct answer is: 0
This quadratic function is in standard form, f(x)=ax2+bx+c.
For every quadratic function in standard form the axis of symmetry is given by the formula x=−b/2a.
In f(x)= -x2 - 2x – 5, a= -1, b= -2, and c= -5. So, the equation for the axis of symmetry is given by
x = −(-2)/2(-1)
x = 2/-2
x = -1
The equation of the axis of symmetry for f(x)= -x2 - 2x – 5 is x = -1.
The x coordinate of the vertex is the same:
h = -1
The y coordinate of the vertex is :
k = f(h)
k = -(h)2 - 2(h) - 5
k = -(-1)2 - 2(-1) - 5
k = -1 + 2 - 5
k = -4
Therefore, the vertex is (-1 , -4)
For finding the y- intercept we firstly rewrite the equation by substituting 0 for x.
y = -(0)2 - 2(0) - 5
y = 0 - 0 - 5
y = -5
Therefore, Axis of symmetry is x = -1
Vertex is ( -1 , -4)
Y- intercept is -5.
The equation of the axis of symmetry for f(x)= -x2 - 2x – 5 is x = -1.
The x coordinate of the vertex is the same:
The y coordinate of the vertex is :
Therefore, the vertex is (-1 , -4)
For finding the y- intercept we firstly rewrite the equation by substituting 0 for x.
Therefore, Axis of symmetry is x = -1
Vertex is ( -1 , -4)
Y- intercept is -5.
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