Question 60013: help on this graph needed, please!
For the quadratic function y= f(x)= x^2-2x-15, find the vertex and x and y intercepts. Sketch the graph, and state the domain and range.
thanks again, carol
Answer by funmath(2933)   (Show Source):
You can put this solution on YOUR website! Hi Carol,
:
For the quadratic function y= f(x)= x^2-2x-15, find the vertex and x and y intercepts. Sketch the graph, and state the domain and range.
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You can find the x coordinate of the vertex of a parabola when the quadratic equation is in the form of  , with the formula 
Your a=1, b=-2, and c=-15
You can find the y coordinate by letting x=1 and solving for y.
The vertex is (1,-16)
:
You can find the x-intercepts, if there are any, by letting y=0 and solve for x. This time you can factor, sometimes you have to use the quadratic formula.
0=(x-5)(x+3)
x-5=0 and x+3=0
x-5+5=0+5 and x+3-3=0-3
x=5 and x=-3
The x intercepts are (-3,0) and (5,0)
:
You can find the y-intercept by letting x=0:
The y-intercept is (0,-15)
The graph looks like this:
Happy Calculating!!!
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