SOLUTION: Can someone please help me with this problem. State whether the paraabola opens upward or downward. f(x)=-x^2-18

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Question 201859: Can someone please help me with this problem.
State whether the paraabola opens upward or downward.
f(x)=-x^2-18
Found 2 solutions by jim_thompson5910, RAY100:
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
Notice that the quadratic f%28x%29=-x%5E2-18 is in the form of f%28x%29=Ax%5E2%2BBx%2BC where A=-1, B=0, and C=-18



Recall that

if A > 0, then the parabola opens upward

if A < 0, then the parabola opens downward


Since A=-1, which is less than 0, this means that the parabola opens downward.


Here's a graph to prove it:





Graph of f%28x%29=-x%5E2-18

Answer by RAY100(1637) About Me  (Show Source):
You can put this solution on YOUR website!
f(x) =y= - x^2 -18
.
(y+18) =-1 x^2,,,,,,std form (y-k) =A (x-h)^2
.
vertex at ( 0,-18)
.
since A is negative, pointing down
.
double check,,graph on either side of vertex
.
x= 1,,,,y=-19
.
x=-1,,,,,y=-19,,,,,therefore pointing down