SOLUTION: The most significant time to be aware of the UV index on a sunny day is modelled by the function f(x)=-0.08(x-13)^2+9 where x is the time of day on a 24 hour clock and f(x) represe

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: The most significant time to be aware of the UV index on a sunny day is modelled by the function f(x)=-0.08(x-13)^2+9 where x is the time of day on a 24 hour clock and f(x) represe      Log On


   



Question 1006172: The most significant time to be aware of the UV index on a sunny day is modelled by the function f(x)=-0.08(x-13)^2+9 where x is the time of day on a 24 hour clock and f(x) represents the uv index.Whats is the UV index at 2 pm? when will the UV index be 7?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
At 2 PM, with 24 hr clock, +x+=+14+
+f%28x%29+=-.08%2A%28+x-13+%29%5E2+%2B+9+
+f%2814%29+=+-.08%2A%28+14-13+%29%5E2+%2B+9+
+f%2814%29+=+-.08%2A%28+1+%29%5E2+%2B+9+
+f%2814%29+=+8.92+
UV index is 8.92
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If UV index is +7+,
+f%28x%29+=+-+.08%2A%28+x-13+%29%5E2+%2B+9+
+7+=+-.08%2A%28+x-13+%29%5E2+%2B+9+
+-.08%2A%28+x-13+%29%5E2+=+7+-+9+
+%28+x-13+%29%5E2+=+%28-2%29%2F%28-.08%29+
+%28+x-13+%29%5E2+=+1%2F.04+
+x+-+13+=+sqrt%28+25+%29+
+x+-+13+=+5+
+x+=+18+
This would be 6 PM on the 24 hr clock