A quadratic function is given. please help

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f(x) = x2 + 8x + 15

(b) Find its vertex and its x- and y-intercept(s). (If an answer does not exist, enter DNE.) 

vertex    (xy) =
  
x-intercepts    (xy) =
  
 (smaller x-value)
(xy) =
  
 (larger x-value)
y-intercept    (xy) =
  


Mar 3rd, 2015

Vertex= (-4,-1) 

Find the vertex by completing the square to convert the quadratic to the form of y=(x-a)^2+K

In this case y= (x+4)^2-1

X intercepts should be found by factorizing. (x+3)(x+5) are the factors in this case. So x=-3 or x=-5 This means when y=0 x=-3 or x=-5. The smaller x value coordinate will then be (-5,0) and the larger will be (-3,0). 


Then to find the y intercept simply plug in 0 for your x value in your original equation. When you solve this you should get y=15 when x=0. So the coordinates would be (0,15)

Let me know if you are still confused! Hope that helps. 

Mar 3rd, 2015

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Mar 3rd, 2015
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Mar 3rd, 2015
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