What i sthe range of the quadratic function F(x)= -5x^2+30x+4 A.) Y49

Question

What i sthe range of the quadratic function F(x)= -5x^2+30x+4 A.) Y<49 B.) Y<3 C.) x>49 D.) Y>49

anonymous · Answer

range is always something with y, so C is wrong.
The range depends on the minimum or maximum of the function. To determine the maximum or minimum of a function, one uses the derivative and sets it to 0.
f(x)=-5x²+30x+4
f'(x)=-10x+30
f'(x)=0
-10x+30=0
30=10x
x=3

Let's fill in x=3 in f(x):
f(3)=-5*3²+30*3+4=-5*9+94=94-45=49
Now, does f(x) have a maximum or a minimum?

anonymous · Answer

si it has to be B

anonymous · Answer

No, f(x)=y
and y=f(3)=49, so the top can't be on y=3.

anonymous · Answer

ohh okay C

anonymous · Answer

Are you just guessing now?
I already stated C was wrong.

anonymous · Answer

ohhh i could swear if > is greater then right

anonymous · Answer

you there i just relize that this is less> and this is greater <so the answer is D