Let the function f(x) be defined by the equation y = f(x), where x and f(x) are real numbers.
f(x) = 4 − x^2

f(9) =
f(-7) =
f(k) =
f(k2 − 8) =

Question

Let the function f(x) be defined by the equation y = f(x), where x and f(x) are real numbers. 
f(x) = 4 − x^2

f(9)  =  
f(-7)  = 
f(k)  =  
f(k2 − 8)  =

anonymous · Answer

f(9)=-77
f(-7)=-45
f(k)=4-k^2

anonymous · Answer

i'm not sure about the last one, sorry

anonymous · Answer

no worries.. how did you get -77? I want to try and understand this

anonymous · Answer

Just put in 9 to the equation so f(9)=4-9^2

anonymous · Answer

Last one is 2k-8? or k^2-8?

anonymous · Answer

i got it.. i was trying to multiply it instead of subtracting it...

anonymous · Answer

:)

anonymous · Answer

andras 2k-8 nor k^2-8 are correct for the final answer ive tried them

anonymous · Answer

hmm, but my question was what is k2 here:  f(k2 − 8)

anonymous · Answer

$$ f(k^2 − 8)  =  $$  is the equation

anonymous · Answer

u just have to put k^2-8 into the function.
So it will be f(k^2-8)= 4-(k^2-8)^2=-k^2+16k-60

anonymous · Answer

and I guess k is just a free parameter here