SOLUTION: Sketch the graph of the quadratic function, indicating the coordinates of the vertex, the y-intercept and the x-intercepts (if any). (Do this on paper. Your instructor may ask you

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Question 354042: Sketch the graph of the quadratic function, indicating the coordinates of the vertex, the y-intercept and the x-intercepts (if any). (Do this on paper. Your instructor may ask you to turn in this graph.)
f(x) = x**2-20 x-800
Vertex
( 1, 2)
y-intercept
y = 3
x-intercepts (Enter solutions from smallest to largest. If there are any unused answer boxes, enter NONE in the last boxes.)
x =
x =
Answer by sofiyac(983) About Me  (Show Source):
You can put this solution on YOUR website!
To find x intercepts you set the equation equal to zero and solve for x.
+f%28x%29+=+x%5E2-20x-800+ factor the equation
+f%28x%29+=+%28x-40%29%28x%2B20%29+
+0+=+x-40+ add 40 to each side
+x+=+40+
+0+=+x%2B20+ subtract 20 from each side
+x=-20+
So the x intercepts are (40,0) and (-20,0).
To find the y intercept you plug in x=0 into the equation and solve for y.
+y+=+x%5E2-20x-800+=+0-0-800=-800+ So the y intercept is (0, -800).
To find the x coordinate of the vertex you use the formula +h+=+-b+%2F+%282a%29+=+20%2F2=10+ Then to find the y coordinate of the vertex, you plug in 10 into the equation and solve for y.
+x%5E2-20x-800++=+10%5E2-20%2A10-800+=+100-200-800+=+-900+ So the vertex is at (10,-900).
Plot x and y intercepts and the vertex and smoothly connect the dots.
+graph%28+300%2C+300%2C+-40%2C+60%2C+-1000%2C+1000%2C+x%5E2-20x-800+%29+